bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurements and Control of Flow Oscillation Induced by a Cylinder Placed in a Two-Dimensional Turbulent Jet
Authors: Fujii Masato , Matsubara Masaharu , Yoshida Takashi , Ikeda Toshihiko , Tsuchiya Yoshiaki
Published: February 2009

An experimental study is presented of the jet flow, effusing with a velocity profile of developed turbulent flow, and of the flow control by means of sound emission. The impinging distance, defined as the distance between the exit and the cylinder, is xi, the slit width h is 10mm, and the cylinder diameter d is 20mm. The exit velocity of two-dimensional turbulent air jet is settled at 20m/s. Measurements include pressures around the cylinder, and the velocity of the jet flow. An oscillation of impinging jet is induced by inserting a cylinder over a range of the impinging distance, 3 < xi/h < 10, even when the jet effuses with a profile of developed turbulent flow. At the impinging distance of xi/h = 8, the oscillation process of mean velocity field is shown by means of the contours of mean velocity and arranged as an animation. The sound emission with the same frequency as that of natural oscillation stabilizes the periodic motion of the original oscillation. The jet flow is controlled to oscillate at a deviated frequency in the case when the intense sound was emitted within an extent of frequency deviation from the natural frequency. The flow with two peak frequencies, observed in the spectrum at xi/h = 10, is also controlled by emitting the sound with either of the frequencies. The free jet, effusing with a profile of developed turbulent flow, might be controlled by various frequencies.
Vortex-Induced Vibrations of Long Marine Risers in Sheared Flows: DNS Studies
Authors: Lucor Didier , Ma X. , Triantafyllou M. S. , Karniadakis G. E.
Published: February 2009

The offshore industry is moving to ever-increasing water depths, producing presently oil in depths of up to 2,500m, requiring detailed fatigue calculations for the risers and tendons used in the floating structures, see [1, 2]. Currents in the ocean are invariably highly sheared, hence the modes that can potentially be excited are many, see [3]. The calculation of how many and which modes are excited, can affect fatigue life very significantly, but there are no guidelines presently available for conducting this calculation.
Modeling Tees and Manifolds in Networks
Authors: Schohl Gerald A.
Published: February 2009

Rigorous modeling of combining and dividing flow through tees improves solutions for steady and unsteady flow in pipe networks dominated by tee losses and in pipe networks, such as navigation lock filling and emptying systems, where distribution of flow through a manifold is of interest. Every tee has two flow paths with different loss, or tee, coefficients for each path. Rigorously modeling a tee means varying the tee coefficients with the split in flow through the tee and accounting for changes in velocity head in each flow path. The general purpose computer code TFSIM provides diverging_tee and converging_tee components for rigorous modeling of tees in pipe networks. A manifold with relatively few branches or portholes can be modeled as a header pipe with a series of tee components spread along its length. However, this approach becomes impractical for manifolds with many, perhaps hundreds, of branches. TFSIM provides diverging_manifold and converging_manifold components that model multiple, identical tees in one component. Several of these manifold components distributed along the length of a header pipe can be used to represent a manifold with hundreds of physical branches. Discharges predicted using manifold components agree closely with those predicted using individual tee components for every branch.
Steady Flow Calculations Using Transient Analysis Combined With Network Analysis
Authors: Shimada Masashi , Kurisu Ryota
Published: February 2009

This paper proposes a method of solving steady flows in large pipelines with the transient analysis (MOC) combined with the network analysis. The existing methods of accelerating the speed of convergence to steady flows in pipelines, i.e., the time marching approach (TMA) replaces the system dimensions (lengths of pipes, friction factors, wave speeds) by not actual ones and dynamically controls one optimization parameter to reduce the spectral radius. That method will be applied to two pipeline systems having a few thousand of pipes. To accelerate much more the convergence the graph-theoretical information used in the network analyses is implemented. From the discharges computed with TMA the heads at each node are adequately modified using the information of “Tree” of the directed-graph defined for pipelines. Two variations of the method are also proposed. They reduces much the Cpu time to solve steady flows in large pipelines.
Physical Simulation of Transient Process in Conduits of Hydropower Stations
Authors: Yang Jiandong , Li Jinping , Tang Yuehao
Published: February 2009

The transient process in the conduits of hydropower stations is a very complicated dynamic procedure coupled with fluid, machines, electricity, and even structure. The current methods used to analyze them separately cannot satisfy the design and the operation requirement of those large underground stations with long conduits. So it is necessary to develop a global physical simulation for the power station transients. As an initial discuss, this article focuses on the introduction of model similarity, model scale and some results about great fluctuation, small fluctuation and hydraulic interference in transient flow experiments.
Dynamic Characteristics of a Check Valve for Drain Pumps
Authors: Sugiyama Hiromu , Mizobata Kazuhide , Ohtani Kiyonobu , Ohishi Takashi , Sasaki Yuji , Musha Hiroyuki , Miwa Toshio
Published: February 2009

Check valves for checking reverse water flows in drainage systems sometimes make large impacts through their sudden closure caused by accidental cutoff of drain pumps. In order to characterize such phenomena and to find design criteria for impactless check valves, we observed the motion of a check valve and measured its impact acceleration and pressures in the drainage pipe, using a subscale drainage system. Two peaks of impact acceleration were observed; The first one seemed due to collision of the check valve and the valve seat, whereas the second one did due to water column separation and recombination caused by the low pressure during the contact of the valve with the seat. The former can be reduced by adding mass to the check valve and by setting an appropriate valve-seat angle. The latter possibly can be reduced by relaxing the low pressure during the contact. Subsequently, the check valve opened through the water-column recombination impacts.
Flashing Hammer Phenomenon in Rapid Liquid-Liquid Contact
Authors: Koga Tatsuya , Takamasa Tomoji , Hazuku Tatsuya , Fukamachi Norihiro , Saito Akira , Aya Izuo
Published: February 2009

In a wall crack accident or loss-of-coolant accident (LOCA) in an advanced reactor with water filled containment, high pressure saturated water is discharged from the pressure vessel into the low-pressure, low-temperature water of the containment. The discharged saturated water causes flashing and generates steam. Steam is then condensed by the water in the containment. This paper describes our study of high pressure saturated water that rapidly contacts low-pressure, low-temperature water. The purpose of the study was to clarify the transient phenomena that occur when high pressure saturated water blows down from a pressure vessel into a water filled containment during a wall crack accident or LOCA in an advanced reactor. The experimental results revealed that flashing of high-pressure saturated water and a subsequent water hammer occurred under the specified experimental settings. Pressure peaked when steam generation or flashing occurred at the wall surface and the flashing steam condensed. After the peak, pressure oscillated and reached equilibrium condition in a short time. The pressure oscillation might have been caused by a balancing action between the flashing of high pressure saturated water and condensation of the steam generated by flashing in low-pressure, low-temperature water. To check the results of the experiments, numerical analyses were conducted. The numerical results cleared the mechanism behind flashing hammer phenomenon.
Measurement of Turbulent Mass Mixing Caused by a Particle Wake
Authors: Koso Toru , Koyama Eiji , Mikamoto Takayuki
Published: February 2009

When a particle moves in a fluid, the fluid is disturbed by the particle and the fluid mass is mixed. This phenomenon is commonly observed in particle-laden flows and dispersed bubble flows. This mass mixing can be composed of two mechanisms. One is the mass transfer by convective flows that are induced by the reaction of the particle drag and the other is the turbulent mass mixing in the turbulent wake of the particle. The effect of the former one can be evaluated using the previous studies on the particle drag. However, the effect of the turbulent mixing is little understood. The turbulent mixing caused by a particle wake is investigated by visualization and noninvasive concentration measurement using a photochromic dye. A sphere brass particle of 5mm in diameter is dropped in kerosene filled in a vertical pipe and the mixing of dye is visualized. The photochromic dye, which is activated by an ultraviolet light, keeps its color in a few minutes after the activation. A part of the fluid is activated without disturbances and is subjected to the mixing by the particle wake. The visualized dye patterns indicate the dye is mixed isotropically by large-scale vortex motions when the particle sheds the vortices. Furthermore, the photochromic concentration measuring (PCM) technique is developed to obtain the concentration of the mixed dye. This PCM technique is based on the Lambert-Beer’s law for light adsorption and provides the average dye concentration along the light path. The measured concentration distribution shows rather isotropic mixing in longitudinal direction. The turbulent diffusion coefficient (TDC) is calculated from the temporal changes in the measured concentration distributions. The evaluated TDC shows strong time-dependency, which is attributed to the change in scale and strength of wake vortices. The TDC is about 104 times larger than the molecular diffusion coefficient at its maximum. The effect of particle Reynolds number on the turbulent mixing is also investigated for the Reynolds number range from 263 to 3290. The observed mixing patterns show a drastic change at the critical Reynolds number on the vortex shedding from the particle. The Reynolds number dependency on the non-dimensional TDC and mixing time are discussed.
A Case Study of International Cooperation: 30 Years of Collaboration in Cavitation Research
Authors: Arndt Roger E. A. , Keller A. P.
Published: February 2009

This paper describes research activities that began after the authors first met at an ASME meeting in Detroit in 1973. Emphasis is placed on the progress in our understanding of the physics of cavitation as influenced by water quality, i.e. the strength of the water as influenced by the concentration of free and dissolved gas. Examples are drawn from three studies, the last of which is still in progress. The paper offers a review of both previously published work and new material appearing in print for the first time.
A New Approach for Determination of Cavitation Sensitivity of Water
Authors: Heller Winfried
Published: February 2009

The conditions for the appearance of cavitation, i.e. the local vaporization of fluid under static or dynamic stresses, are closely connected with the tensile strength of the fluid (Arndt, Keller (1992)). Although the dominant effect of water quality on the cavitation interception has been known for many years (Keller (1981, 1983, 1984)), it is uncommon to measure its stress resistance. A possible reason for that could be the unique stress-resistance probe of Keller (1987, 1994) (Eickmann (1992)), which by itself represents a great engineering break-through, is rather complex and expensive. It has become clear during the ASME/JASME conference in San Francisco, 1999 (Keller, Rott, Striedinger, Awad, Ludwig, Yang, Li), and the Fourth International Symposium on Cavitation in Pasadena 2001 (Keller), that internationally standardized testing conditions are required with respect to water quality (Heller (2000)). A relatively simple method of concurrently measuring tensile strength or cavitation susceptibility in cavitation channels has been developed at the Institute of Fluid Mechanics of the Technische Universita¨t Dresden during the last months. This newly developed tensile strength measuring technique is not only efficient and cheap but can also be installed in any existing cavitation channel with comparably small effort. The presented paper represents the actual developmentstate of the Dresden measuring device. Comparison measurements at the cavitatio n-channels of the Versuchsanstalt Obernach (Dr. Keller), Schiffsbau-Versuchsanstalt Potsdam (Mr. Heinke) and the Schiffsbau-Versuchsanstalt Hamburg (Mr. Friesch) are planed for the following months.
Noise Due to Extreme Bubble Deformation Near Inception of Tip Vortex Cavitation
Authors: Choi Jin-Keun , Chahine Georges L.
Published: February 2009

A study on the tip vortex cavitation inception based on extreme bubble deformation and jet noise is presented. First, two preliminary experiments are performed to provide a correlation between the numerically computed splitting/jet noise and the measured noise. The bubble behavior and pressure signal predicted by the axisymmetric method are compared with those recorded simultaneously by using a high-speed video camera and hydrophone. Then, numerical studies on the bubble behavior in the tip vortex flow field are conducted. The tip vortex flow near a hydrofoil is provided by a viscous flow computation, and the bubble behavior is simulated by an axisymmetric boundary element method based on the provided vortex flow field. The characteristics of the bubble behavior and jet noise over a range of cavitation numbers are investigated. The effect of initial bubble nucleus size and the Reynolds number effect of the tip vortex flow on the tip vortex cavitation inception, the bubble behavior including its splitting, and jet noise are also discussed.
Computation of Cavitation Inception Number for Surface Irregularities
Authors: Amromin Eduard
Published: February 2009

Computation of cavitation inception number for isolated surface irregularities is performed with the assumption that cavitation bubbles appear in vortices located within viscous separation zones behind these irregularities. The numerical analysis consists of four parts. The first part is determination of the base pressure within separation zone and irregularity drag by using viscous-inviscid interaction concept for an obstacle in non-uniform incoming flow. This part is validated by the well-known experimental data for cavitation-free flows behind backward-facing steps and within specially designed wind tunnels (by Tani et al {1] and Agarwal & Simpson [2]). The second part is determination of vortex intensity by using the base pressure and drag in an empirical formula. The third part is determination of vortex viscous core from an asymptotic solution of Reynolds equation for the vicinity of a vortex in the turbulent flow. The fourth part is calculation of cavitation inception number for a bubble with taking into account the surface tension effect. The suggested theoretical concept and numerical technique are validated by comparison with measurements for irregularities over flat walls and 2D hydrofoils (by Arndt et al [3] and Holl et al [4]).
Scaling of Tip Vortex Cavitation Inception Noise With a Bubble Dynamics Model Accounting for Nucleus Size Distribution
Authors: Hsiao Chao-Tsung , Chahine Georges L.
Published: February 2009

A Surface-Averaged Pressure (SAP) spherical bubble dynamics model accounting for a statistical nuclei size distribution was used to model the acoustic signals generated by cavitating bubbles near inception in a tip vortex flow. The flow field generated by finite-span elliptic hydrofoils is obtained by Reynolds-Averaged Navier-Stokes computations. An “acoustic” criterion which defines the cavitation inception by counting the number of acoustical signal peaks that exceed a certain level per unit time was applied to deduce the cavitation inception number for different scales. It was found that the larger scale results in more cavitation inception events per unite time because more nuclei are excited by the tip vortex at the larger scale. The nuclei size was seen to have an important effect on cavitation inception number with scaling effects due to nuclei increasing as nuclei sizes decreases.
A Proposal for Modeling Intermittent Transitional Pulsatile Flows
Authors: Berger Stanley A. , Younis Bassam A.
Published: February 2009

The principal requirements in a turbulence model to be valid for the prediction of arterial flows are the ability to capture the consequences of laminar–turbulent transition that occur at various phases of the cardiac cycle and to yield accurate predictions of the wall shear stresses. These requirements are not immediately met by the majority of turbulence models since these have largely been formulated with reference to data from fully turbulent flows in approximate local equilibrium. The purpose of this paper is to report on recent progress in the development of a turbulence model that overcomes some of these limitations. The model is based on the solution of transport equations for two turbulence parameters that are zero–valued at a solid wall and an additional equation for intermittency. Comparisons with measurements obtained in oscillatory transitional flows in circular pipes show substantial improvements over existing closures.
Review of the Secondary Flows of Complex Fluids
Authors: Siginer Dennis A.
Published: February 2009

A survey of secondary flows of viscoelastic liquids in straight tubes is given including recent work pointing at striking analogies with transversal deformations associated with the simple shearing of solid materials. The importance and implications of secondary flows of viscoelastic fluids in heat transfer enhancement are explored together with the difficulties in detecting weak secondary flows (dilute, weakly viscoelastic solutions) in a laboratory setting. Recent new work by the author and colleagues which explores for the first time the structure of the secondary flow field in the pulsating flow of a constitutively nonlinear simple fluid in straight tubes of arbitrary cross-sections is summarized. Arbitrary conduit contours are obtained through a novel approach to the concept of domain perturbation. Time averaged, mean secondary flow streamline contours are presented for the first time for triangular, square and hexagonal pipes.
Prediction of Heat Transfer Rates in Shear Flows With Streamline Curvature
Authors: Younis Bassam A. , Berger Stanley A.
Published: February 2009

Gradient–transport models for the turbulent scalar fluxes have proved to be deficient in a number of important practical flows, especially in those where the effects of body forces and extra rates of strain are significant. There are numerous examples in this respect, most notably in the prediction of the heat transfer rates in flows where the effects of stabilizing streamline curvature are sufficiently strong to completely extinguish turbulent mixing. The cause of the problem appears to be in the omission from these models of an explicit dependence of these fluxes on the mean strain field — a dependence that is required by the exact equations that govern the evolution of the turbulent scalar fluxes. The purpose of this paper is to determine whether the incorporation of such dependence in an algebraic model for the turbulent scalar fluxes is on its own sufficient to capture the main effects of streamline curvature. The model used here is an explicit, non–linear model that was developed in collaboration with the late Professor Speziale (Younis, Speziale & Clark, 1996). It is first validated in this paper by comparisons with data from one– and two–dimiensional heated free shear flows and is then used to predict the main features of a heated homogeneous shear layer in local equilibrium. Comparisons made with experimental data and with other models demonstrate the validity of the present approach.
Non-Canonical Jets-in-Crossflow
Authors: Plesniak Michael W.
Published: February 2009

This invited paper presents a review of research done over the past several years at Purdue on non-canonical jets-in-crossflow. It is a retrospective and an integrative compilation of results previously reported as well as some new ones. The emphasis is on jets emanating from “short” holes, with length-diameter ratios of one or less. These are non-canonical in the sense that the flow is unable to “adjust” to the hole, unlike that in case of a long hole in which fully developed pipe flow can be attained. This motivated by gas turbine film cooling applications. Experimental results acquired with Particle Image Velocimetry will be presented primarily, with some complementary information gained from RANS simulations of the flow. Many different aspects of the problem have been investigated, and in this paper the focus will be on structural features within the hole and in the developing jet and crossflow interaction. A significant result is that the in-hole vertical structures, depending on their sense of rotation, tend to augment or weaken the primary counter-rotating vortex pair. This impacts global features such a jet trajectory and spreading.
Large-Eddy Simulation of a Turbulent Boundary Layer With Blowing
Authors: Bataille Franc¸oise , Brillant Guillaume
Published: February 2009

The modifications of a turbulent boundary layer induced by blowing through a porous plate are investigated using large-eddy simulation. The Reynolds number (based on the length of the plate) of the boundary layer is about 850,000. In order to simulate the fully developed turbulent boundary layer, an instationnary inflow condition is used. Influences of the fluid injection rate upon the three components of the velocity are characterized and a good agreement is obtained when comparing with previous experimental measures. Evolution of the mean and root-mean square parts of the velocity with injection rate is studied. It is observed that the maximum of the fluctuations of the longitudinal velocity slowly increases with blowing but the size of the domain where the fluctuation level is high, rapidly grows. For the vertical and transverse components, the fluctuating profiles are almost multiplied by two. Finally, blowing is shown to increase the level of the near-wall structures as well as the physical space where they develop.
Contribution to Single-Point-Closure Reynolds-Stress Modelling of Inhomogeneous Flows
Authors: Gerolymos Georges A. , Vallet Isabelle
Published: February 2009

The purpose of this paper is to present recent advances on the development of fully single-point-closure Reynolds-stress models, for flows with strong inhomogeneities, such as solid-wall effects or strong streamwise gradients (eg. shockwave/turbulent-boundary-layer-interaction). As a starting point it is shown that several recently developed wall-normal-free (wall-topology-free) RSMs, using gradients of turbulence length-scale and of anisotropy-invariants to replace geometric normals, can be interpreted as a generalization of well-known redistribution closures but with coefficients that are not scalars but fourth-order tensors. These tensorial coefficients are function of anisotropy-invariants and of their gradients (which indicate the direction of inhomogeneity). In view of the above result, it is suggested that the theory of the redistribution tensor closure should be revisited, with emphasis on inhomogeneity effects. Four baseline sets of coefficient values are given, and the proposed models are applied for various flows (developing flow in a square duct, 2-D and 3-D separated flows).
One-Equation Subgrid Scale Model Using Dynamic Procedure for the Energy Production
Authors: Kajishima Takeo , Nomachi Takayuki
Published: February 2009

The transport equation of subgrid scale (SGS) kinetic energy, KSGS, is used for the large-eddy simulation (LES), considering its possible consistency with dynamic procedure. The smallest scale portion in computationally resolved turbulence, which is estimated in the dynamic model, has closer relationship with largest scale in SGS. Therefore the dynamically determined parameter is more suitable for describing the energy transfer between resolved and SGS turbulence, rather than the energy dissipation through the SGS eddy-viscosity in the filtered equation of motion. Such an energy transfer is represented by the production term in the transport equation of KSGS in our model. Computational examination has been conducted for fully developed turbulent flow in a plane channel. Agreement with DNS database was fine and it was improved by refining the grid.
An Investigation of the Aerodynamic Response of a Wind Turbine Blade to Tower Shadow
Authors: Munduate Xabier , Coton Frank N. , Galbraith Roderick A. McD.
Published: February 2009

This paper presents results from a wind tunnel based examination of the response of a wind turbine blade to tower shadow. In the experiment, one of the blades of a two-bladed, downwind turbine was instrumented with miniature pressure transducers to allow recording of the blade surface pressure response through tower shadow. The surface pressures were then integrated to provide the normal force coefficient responses presented in this paper. It is shown that it is possible to reproduce the measured responses using an indicially formulated unsteady aerodynamic model applied to a cosine wake velocity deficit. It is also shown that agreement between the model and the measured data can be improved by careful consideration of the velocity deficit geometry.
Prediction of Flow Distribution in Gas-Liquid Two-Phase Annular Flows in a Rod Bundle Under Hydraulically Equilibrium Condition
Authors: Kawahara Akimaro , Sadatomi Michio , Aoyama Nobutaka , Tanoue Satoru
Published: February 2009

Subchannel flow distributions of both gas and liquid phases under a hydraulically equilibrium condition have been investigated experimentally and analytically for two-phase annular flows in a vertical channel simulating a BWR fuel rod bundle. In the experiment, data on two-phase flow rates in subchannels were obtained for several equilibrium annular flows. In the analysis, a simple, one dimensional, one pressure, two-fluid model has been applied to calculate the flow distributions. In addition, an equation of identical-wall-shear-stress between subchannels was incorporated as a closure equation for the analysis. From a comparison between the calculation and the experiment, the present analysis was found to be promising.
Bubble-Driven Convection Around Cylinders Confined in a Channel
Authors: Murai Yuichi , Sasaki Toshio , Ishikawa Masa-aki , Yamamoto Fujio
Published: February 2009

This paper concerns with flow visualization and image measurement of bubbly flows around various shapes of cylinders. A coaxial confined double rectangular chamber is constructed in order to provide a wide two-dimensional uniform bubble distribution upstream of the obstacle. The experiment shows that a wide two-phase convection is induced around the obstacle, though such an effect is not observed in research on the single-phase flow around objects. The spatial scale of the two-phase convection depends sensitively on the shape of the obstacle. Dense arrangement of cylinders is also investigated to find the interaction among the convection. The measurement results of void fraction, bubble velocity and liquid phase flow, which are obtained by image processing including particle tracking velocimetry (PTV), explore the detailed mechanism of generating the convection.
The Effects of Forced Vibration on Two-Phase Flow in a Small Diameter Tube
Authors: Kariyasaki Akira , Ousaka Akiharu , Fukano Tohru , Kagawa Masazumi
Published: February 2009

The effects of forced vibrations on the motion of air-water two-phase mixture were studied in 2.4mm I.D. horizontal tube over rather wide range of flow conditions (about 60 flows for lateral vibration, 4 flows and 1 stagnant mixture for longitudinal vibration). 13 different modes of sinusoidal vibration with 1–8mm amplitude and 1–7.7 Hz frequency were exerted on the test tube. Pressure drop, void fraction and flow pattern of the two-phase flow were compared to those of the flow without forced vibration. It was made clear that the lateral vibration exerted on the tube induced a self exciting fluctuation of the pressure drop for a specific flow condition and longitudinal vibration on the tube promoted the bubble coalescence.
Study on Single Bubble Chains in Stagnant Water
Authors: Sanada Toshiyuki , Watanabe Masao , Fukano Tohru
Published: February 2009

The behaviors of single nitrogen gas bubble chains, with diameters of from 0.5 mm to 2.5 mm, in stagnant water were experimentally studied. We developed an innovative acoustic bubble generator, which can precisely control both bubble diameter and generation frequency in an independent manner. We discuss the effects of interactions between bubbles in bubble chains on the behaviors of each bubble quantitatively, comparing to those of single rising bubble. Bubble trajectories and surrounding water flow field generated by the bubble chains were carefully investigated by applying the image processing technique to the high-speed video camera data. We analyzed the experimental data and identified the following two significant physical phenomena. (1) Under the condition of bubble radii kept unchanged, while bubbles passed almost the same path in the current measurement region in the case of low generation frequency, they deviated from this path and scattered about 30 mm from the generator with the increase of bubble generation frequency. (2) With higher bubble generation frequency, characteristic structures of the surrounding flow fields were clearly observed. These flow fields possessed the planer structure which could be spanned by the bubble trajectory direction and vertical axis through bubble generator.
Inverse Design of 3D Compressor Blades With Adjoint Method
Authors: Chung June , Shim Jeonghwan , Lee Ki D.
Published: February 2009

A three-dimensional (3D) CFD-based design method for high-speed axial compressor blades is being developed based on the discrete adjoint method. An adjoint code is built corresponding to RVC3D, a 3D turbomachinery Navier-Stokes analysis code developed at NASA Glenn. A validation study with the Euler equations indicates that the adjoint sensitivities are sensitive to the choice of boundary conditions for the adjoint variables in internal flow problems and constraints may be needed on internal boundaries to capture proper physics of the adjoint system. The design method is demonstrated with inverse design based on Euler physics, and the results indicate that the adjoint design method produces efficient 3D designs by drastically reducing the computational cost.
Laboratory Analysis of Momentum-Induced Chokes in Free Surface Flow
Authors: Parr Alfred D.
Published: February 2009

The laboratory exercise described herein allows undergraduate fluid mechanics students to observe and perform experiments on an interesting and pertinent free surface flow phenomenon. A momentum-induced choke is created when lateral inflow enters a hydraulically steep channel at a volumetric rate that is sufficient to induce a choke condition. The choke condition creates a hydraulic jump that may move upstream and drown the channel inlet section. This situation can occur at inlets in storm sewer systems. The project requires students to derive an analytical equation giving the critical lateral inflow rate as a function of approach flow conditions. They also perform a series of flume experiments that produce empirical data for comparison with the theoretical equation.
Teaching CFD: Combining Experiments and Practical Projects With Numerical Simulations
Authors: Guessous Laila
Published: February 2009

This paper describes two projects assigned to students in a senior/beginning graduate level course on Computational Fluid Dynamics (CFD) at Oakland University. One of the novel features of this course is a class project that combines a laboratory experiment with a CFD flow analysis. This project involves pressure and velocity measurements in a venturi device in a wind tunnel apparatus and their subsequent comparison to CFD simulation results for the same geometry using the commercial CFD software Fluent®. A second project, “Turbulent Flow Through a 90-degree Elbow,” involves the use of CFD simulations to propose an explanation for and possible solution to the erratic behavior of a paddle-type flow detection switch placed in a 90-degree bend to detect the presence of air flow in the circular duct. Details of these class assignments, as well as results and lessons learned from this course experience are discussed.
Compressible Flow Simulations Over Basic Reusable Rocket Configurations
Authors: Fujimoto Keiichiro , Fujii Kozo
Published: February 2009

Compressible flow around the basic reusable rocket configurations are numerically simulated by Navier-Stokes computations. The study started with the simulations of Apollo configuration to validate the simulation method by the comparison of the aerodynamic data with NASA’s experiments, and the capability of CFD estimation are discussed. Computed aerodynamic coefficients for the Apollo agreed well with the experiments at subsonic to supersonic flow regime for whole angle of attack range. Then, the effects of the configuration parameters on the aerodynamic characteristics are numerically investigated and clarified in detail. It turns out that the aerodynamic characteristicsismainlyinfluenced by the separating position of the flow, shock wave on the surface and the pressure level behind the body. Large shoulder radius causes the strong Mach number dependency of the aerodynamic characteristics, and large fineness ratio strongly influences to the (CL)max.
Computational Analysis of Turbulent Flow Around a Dimpled and Smooth Sphere
Authors: Alammar Khalid N.
Published: February 2009

Steady turbulent flow around a 43-mm diameter smooth sphere and one with 245 round dimples was simulated. The turbulent flow around the sphere was attained by placing a turbulator 9 mm’s upstream of the center point. For comparison, the turbulator was also placed around the dimpled sphere. The simulation revealed stable vortical flow structure inside the dimples. A stable vortex pair in the wake region was predicted in both cases. Predicted separation point over the smooth sphere was further downstream than in the case of dimpled sphere. The predicted drag coefficient for the smooth sphere was 40% lower than that of the dimpled sphere, which was 0.35. Drag predictions are compared with previously published measurements.
Numerical Study on Preliminary Thermal Mixing Test in B&C Loop Facility
Authors: Kang H. S. , Kim Y. S. , Park C. K. , Cho S. , Song C. H.
Published: February 2009

The benchmark calculation for a preliminary thermal mixing experiment in the B&C Loop facility was performed to develop a thermal mixing model in quenching tank using CFX4.4. A steam discharge through the sparger and the condensation phenomenon were modeled with the choking flow and the condensation region model to generate the velocity and the temperature of the condensed water for the boundary condition of CFX4.4. The transient calculation results at about 30 seconds show a good agreement to the temperature distribution with that of experiment. Therefore, we can anticipate that CFX4.4 with the condensation region model can simulate the thermal mixing behavior in a quenching tank when the steam is discharged. And also, we can expect that the numerical model for the thermal mixing taking place for a long time in the IRWST of APR1400 may be developed by this method.
Modeling on the Effect of Imbalance Burner Pressure and Mass Flow Rate in a Full-Scale Gas Fired Industrial Boiler
Authors: Hasini Hasril , Yusoff Mohd. Zamri , Majid Kamsani Abdul , Ramli Mohd. Rizal , Hassan Hamdan , Hussein Ibrahim , Boosroh Mohd. Hariffin
Published: February 2009

CFD simulation of the combustion process in a 120MW gas fired industrial boiler has been performed, with focus on the flow pattern and temperature distribution at the reheater section in the furnace. The modeling was done using general-purpose CFD software, CFD-ACE+ developed by CFD Research Corporation. The effect of imbalance burner pressure is simulated by varying the mass flow rate of fuel (natural gas) injected at each burner. The simulation result shows good qualitative agreement with practical observation. The flow in the furnace is highly swirling with intense mixing and follows a helical pattern in an anticlockwise direction. Temperature distribution prior to entry to the reheater is significantly higher on the right side of the reheater. As a conclusion, the imbalance nozzles pressure creates uneven mass flow rate of air and fuel, which results in asymmetric flow pattern and temperature distribution at the reheater section.
Large Eddy Simulation of Turbulent Channel Flows Using GSMAC-FEM
Authors: Miyoshi I. , Tanahashi T.
Published: February 2009

In this study, the parallel scheme for LES (Large Eddy Simulation) with GSMAC-FEM is constructed. In terms of the application of the Computational Fluid Dynamics (CFD) to the practical problems, the parallel FEM scheme is thought to be promissing. Before applying it to the practical problems, it is necessary to examine the effectiveness of the parallel scheme through the benchmark problem which other researchers have examined. In this study, turbulent channel flow at Reynolds number Reτ = 1180 based on the friction velocity and channel width is analyzed, and numerical results are compared with the DNS data. Through the results, the present scheme is verified. The representative SGS model, the Smagorinsky model, is applied at the first step. The parallelization of GSMAC-FEM is conducted with the distributed multiprocessor, and the effectiveness is discussed in terms of the large scale calculation.
Effects of an Upstream Circular Manipulator on the Flow Past a Cylinder-Flat Plate Junction
Authors: Dow Alan , Elizarraras George , Rahai Hamid R. , Hefazi Hamid
Published: February 2009

Measurements of three components of mean velocity and simultaneous time-resolved measurements of axial and vertical turbulent velocities and their cross moment were made at three perpendicular planes slightly upstream of the corner and in the downstream interaction region of a cylinder-flat plate junction with and without an upstream circular manipulator. The circular manipulator was a smooth circular cylinder of 1.25 mm diameter, which was placed upstream of the cylinder at X/D = 1.2, within the boundary layer above the flat plate surface. Results show that when the manipulator is in place, there is a decrease in the axial mean velocity and increases in the axial mean squared turbulent velocity and turbulent shear stress at the first plane. There is an expanded region of secondary flow with reduced circulation, indicating that the manipulator has reduced the strength of the horseshoe vortex in this region.
Effects of Periodic Holes on the Suppression of Aeroacoustic Noise From a Pantograph Horn
Authors: Takaishi Takehisa , Ikeda Mitsuru , Kato Chisachi
Published: February 2009

Three types of pantograph horn model; simple cylinder, a cylinder with periodic holes and a cylinder with a continuous slit, are tested in a low noise wind tunnel to compare their characteristics of aerodynamic noise and flow fields in the wake. Formation of strong vortices of alternate sign that have large structure in the spanwise direction is suppressed due to the flow through holes or the slit. The cylinder with the continuos slit is proved to reduce the noise sufficiently, but an unstable flow through the slit seems to produce distinct noise. Since formation of strong vortices is mainly suppressed due to momentum injection through holes or the slit, periodic holes have little effect on collapsing the spanwise structure of vortices, but they contribute to making the flow around the horn stable. The shape of holes should be optimized to avoid strong acoustic resonance.
Aerodynamic Noise and Flow Visualization Around an Inclined Circular Cylinder
Authors: Haramoto Yasutake , Hirao Munetake , Shingai Mitsuru , Ohba Hideki
Published: February 2009

We measured the aerodynamic noise generated from an inclined circular cylinder with endplates in experimental conditions using a low noise wind tunnel. The inclination-angle dependency of the aerodynamic sound is related to the aspect ratio A that is the ratio of the distance between the endplates to the circular cylinder diameter. To analyze the dependency in detail we derived the correlation length from the velocity fluctuation in the wake. As a result, when the inclined angle changed from 0 degrees to 20 degrees, the correlation length got smaller at A = 10. On the other hand, in the case of A = 30, the correlation length got longer. So we visualized the flow around the cylinder using numerical simulation and the hydrogen bubble method in order to analyze these phenomena.
CFD-Based Simulation of Inlet Unstart Phenomena: Toward Supersonic Inlet Flow Control Techniques
Authors: Miller Daniel N. , Smith Brian R.
Published: February 2009

A time-accurate, full Navier-Stokes, Computational Fluid Dynamics (CFD) analysis of a back-pressure-induced, high-speed inlet unstart event was conducted. The objective was to identify visible and quantitative flowfield characteristics prior to and during an unstart event. The CFD-based investigation was conducted on a 2-D wind-tunnel model geometry of a forebody and inlet at a freestream Mach number of 5. A sequence of steady-state solutions were run to map the inlet flowfield response to subsequent increases in back-pressure from a design value up to the point of imminent unstart. A time-accurate solution commenced, using the final steady-state solution as the initial condition. The CFD-derived inlet flowfield contour plots compared well with test-derived color schlieren images, while predictions for steady-state and transient wall pressure compared reasonably with test data. A CFD-based study of inlet flow control techniques will follow.
Engineering Clinic Program (ECP): Its Roles in the Engineering Education in Japan
Authors: Furuya Okitsugu
Published: February 2009

The Department of Basic Engineering in Global Environment (DBEIGE) of the Kogakuin University started only six years ago with the objectives of educating its students to become global engineers. The essential requirements set forth in DBEIGE as the global engineer include 1) the communication skills, 2) the international sense and knowledge, 3) creative thinking, and 4) management skills in addition to the strong basic and specific scientific and engineering knowledge. ECP has been established as one of the key courses in DBEIGE to teach and enhance the four elements described above. It is essentially an industry-university collaborative program where the project themes are provided by the industry together with their technical liaisons. With this new educational program first in its kind in Japan, the graduates seem to be better trained in terms of communicating, thinking globally and creatively, and managing things well than those from the conventional engineering institutes in Japan.
Recommendations for the Long-Term Success of Industrial Collaboration in Engineering Training Programs (Keynote Paper)
Authors: King Joe A.
Published: February 2009

The Engineering Department at Harvey Mudd College developed an industrial sponsored engineering training program in the mid 1960’s. The program now called “The Clinic” is a central part of Harvey Mudd College. Over the years, representatives from a number of colleges have visited our campus in an effort to learn about the program and implement similar programs at their home institutions. The efforts to duplicate the HMC Clinic Program at other institutions have met with varied success. The reasons for the less than perfect success rate are discussed and guidelines for developing a firmly anchored program with potential for long-term survivability and growth are discussed.
Design of a Microcontrolled Water Fountain
Authors: Shakerin Said
Published: February 2009

Water fountains have been used for thousands of years for utilitarian and aesthetic purposes. The design of a fountain provides an excellent opportunity as a multidisciplinary project for engineering and art students. In this paper, detailed design of an indoor fountain with a special effect feature is presented. Comprising of nine individual jets, the fountain produces letters of the alphabet, simple shapes, and symbols with water jets. A microcontroller is programmed to create and sequence through interesting arrangements of water displays. With a total material cost of $550, this design, or variations of it, can be adopted for various implementations in fluids and design courses. Suggestions for student design projects are also made.
Classification of Particles Settled Under a Body of Water
Authors: Nozaki Tsutomu , Arima Kohei , Noguchi Susumu
Published: February 2009

As one of the proposals of a classifier, the injection port is mounted at the collecting mouth where the sands (relatively large particles) and the sediments (relatively small particles) mixture, which pile up under a body of water are fluidized before they are removed. The maximum diameter of the sediments to be removed is only determined by the active control of the vertically upward velocity of water at the classifying region of the classifier. Whether the particle goes up or down in the classifying region depends upon the balance of forces acting upon the particle. In this paper, in order to clarify the characteristics of the classifier traversing it in the horizontal direction, the experiments are carried out using the flow visualization technique, especially, at the beginning of cleaning. As a result, there exists the combination of the smaller and larger beads, which shows the quickest classification performed for the given conditions. The experiments are also carried out for the various flow rate ration of the injection to the suction.
The Effect of Flow Pattern of Slurry Flow on Pressure Loss in Horizontal Pipes
Authors: Sato Hiroshi , Cui Yushun , Yamaguchi Shinji , Sato Isamu , Nakazawa Atsushi , Adachi Hiroyuki
Published: February 2009

The purpose of this paper is to develop a reliable design tool for predicting the pressure loss based on a theoretical model in which the condition factor (a degree of homogeneity) represents flow patterns and is correlated with the geometric parameter of concentration distribution curves. By using the model the effect of the system’s variables and the properties of the solids on the Durand’s φ–φ plot, an obvious relationship between the head loss parameter and the modified Froude number, of computed pressure loss can be explained.
Hydrodynamics of Multiple Size Particles in a Liquid Fluidized Bed Classifier
Authors: Gera Dinesh , Syamlal Madhava , O’Brien Thomas J.
Published: February 2009

A two fluid model is extended to an N-phase, multi-fluid model, in which each particulate phase represents a collection of particles with identical diameter and density. The current N-phase model is applied to a fluidized bed classifier with six different particle sizes to investigate the effects of different operating conditions—fluidizing liquid flow rate, feed voidage, and particle size distribution in the feed stream—on the particle size distribution inside the classifier and the discharge streams. The predicted volume fraction of different particle sizes is compared with the experimental data reported by Chen et al. (2002) for two columns, 191 mm and 292 mm in diameter, each having different geometries and containing glass beads of different sizes fluidized with water. A fairly good agreement is observed between the measured and predicted values for mono- and poly-dispersed systems.