Flow Around Complex Natural Shapes Encountered in Food Processing
Authors: Giorges Aklilu T. G. , Srinivas Saikamal , Haynes Comas , Thomas Sean 
Published: January 2022

Abstract
Flow around complex 3D geometries are of great importance to the processing industry. Particularly in the food processing industry, the shape of product is highly complex, therefore simple 3D geometry flow arrangements cannot fully represent the developing flow dynamics. Furthermore, in industry, processing systems such as washing, disinfecting, and chilling are closely compact in terms of footprint, and the flow dynamics is not only affected by the shape complexity of the product, but also the relative placement of the product. Study of flow around bluff bodies has been a long-standing field of interest for developing insights into various engineering and industrial applications such as heat exchanger design, aircraft design, and wind turbines. Furthermore, bluff body flow dynamics has also extended to a series arranged inline as a call to study the aerodynamics, wake formation, and vortex shedding differences from single cylinder configurations. However, few publications exist that involve the aforementioned situation encountered in food processing industry where complex geometries found in nature are closely placed in fluid stream, and the corresponding flow dynamics are studied. In this work, we numerically simulate the three-dimensional flow field encountered in food processing where a product with complex geometry is suspended in isolation and in series within a flow stream during transport, cleaning, disinfecting, and cooling or heating. Using the industry operating parameters and the complex natural shape of the product, the three-dimensional model of the system was created, and the flow parameters encountered during standard processing are applied. The actual product used in the study is marginally simplified without significantly losing practicality. Regarding the test domain, the channel width and height are 60.96 cm and 46.99 cm, respectively, and the total flow domain length is 6.78 m that includes the test region length of 31.56 cm, an inlet region of 2.12 m before the bluff body, and 4.25 m trailing region after the bluff body. Additionally, the open channel processing flow boundary condition is simplified by using a free-surface, slip boundary condition. In this work, we present our three-dimensional simulation of the complex-shaped product in addition to a mesh study of a simple bluff body and comparable published works detailing similarities and differences. When a bluff body experiences a crossflow, the key points of observation are the location of stagnation points and flow separation as well as wake formation and vortex shedding phenomena. Boundary layer development initiates at the stagnation point and continues along the body surface until an adverse pressure gradient leads to boundary layer or flow separation. Formation of a wake with high vortex incidence ensues and forms a lower pressure region in comparison to the high pressure distribution on the leading side of the body, leading to a net drag force on the bluff body. Examination of these phenomena will be the focus of the numerical study. Furthermore, we will identify and outline the ways to optimize processing using our findings and its implication on food processing as a whole.