Document: NRC Regulatory Guide
Document ID: f4c5fb1d-efb9-4168-9804-5ad3f6f64d06
Document Type: regulatory_guide
Title: Reporting Procedure for Mathematical Models Selected To Predict Heated Effluent Dispersion in Natural Water Bodies
Source: NRC Regulatory Guide Division 4
Source URL: https://www.nrc.gov/docs/ML0037/ML003739535.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-4.4
CFR Part: 
CFR Title: 

Content:
hydrodynamic and thermodynamic equations that govern thermal dispersion having been discussed, it is desirable to review the methods most frequently applied to solve those equations For the most part, such methods tend to be consequences of the scale size and simplifying approximations used to construct the model. The following discussion deals with common solution techniques as they are applied to the spatial dispersion fields of thermal discharL a. Nwe-Field Modeling The case of a buoyant axdsymmetric jet discharging into a cross-flowing ambient stream, while representing only one of a variety of possible discharge configurations, contains the important dynamical processes and illustrates the bac assumptions and techniques generally used in ner-field modeling. The transformation of Eqs. (3.9) through (1&14) into simpler forms suitable for the axisymmetric jet is straightforward but tedious and is not shown here. A complete derivation of the governing equations has been given by Hint,4 whose notation, with slight modification, is used, below. The important point to note is that the near-field approximation is basically equivalet to the Pradti boundary War ap•roimation applied to free turbulent shea flows, viz,, utmemwlse gradients are much smaller this raa gradients, streamnwise velocitf are much' Iager thea rdi velocities, and the deviation from hydrostatic pressumre is approximately constant throughout the jet. Subject to these approxisnations, the conservation equations may be written in a natural cylindrical coordinate system (sr) denoting the local axial and radial directions, rspectively. The angular dependence does not appear since the jet is axisymmetric. The equations of conservation of moss, heat energy, and axial momentum become +f I a a + V)= 0 aT _a= ia.-. uTs- +V - Thrv., (B-23) (B-24) 4E. A. Hirt, "Analysi of Round, Turbulent, Buoyant Jets Discharged to Flowing Ambients,' ORNL-4685, Oak Ridge National Laboratory, 1971. •au• vau [• 1, (,•.ll