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:
l momentum equation. A simple scale analysis indicates that the hydrostatic assumption is generally a valid approximation except possibly in the treatment of high-velocity discharges, in which cae the pressure field has a dynamic contribution that is not necessarily small compared with the hydrostatic component. In general, then, the vertical pressure gradient in Eq. (B3-13) may be written P0 ax 3 p -g + lop * P0 P 8x3 where P is the difference between the actual pressure and the hydrostatic pressure, and p. g is the gradient of hydrostatic pressure. Substitution of Eq. (8-18) into Eq. (B-13) results in a vertical equation of motion in which buoyancy is contained explicitly in the gravity term: a%+ Uj. = -J a-xj I ax 2_P a3 (_ ax Pp- --- g + -(~g an initial velocity Vo moves in an inertia circle in the absence of external forces and confining boundaries. The radius of the inertia circle at mean latitude 0o is Vo/2113sin 0o. The time required for the water to move around the circle (i.e.. period) is 21r2/N3 sin~O. If. for a particular problem, the distance and time scales ot interest are small compared with the circumference and period of the local inertia circle, ro.rational effects maý be neglected. In the near-field, neglect of the Coriolis force is a valid approximation. In the far-field, Coriolii effects might become noticeable as a cum sol deflection of the thermal plume. The practical importance of the latter depends upon the lateral dimensions of the receiving water and the time scale of temperature decay relative to the inertia period. e. Heat Exchange Coefficient Equation (3-14) must satisfy the boundary condition that the heat flux is continuous across the water surface. On the basis of Eq. (B-1 7), this boundary condition may be written D3 a3 =0 = surface heat flux. As discussed in Appendix A, the surface heat flux is taken to be proportional to the product of a surface heat exchange coefficient K and the difference between the actual temperature of the