The equation describing heat loss from the free surface of a well- 

 mixed body of water with an artificial heat input is (Stolzenbach, 1971; 

 Zitta and Douglas, 1975) 



pcv|^ = -KA(T-Tg) + H (3-20) 



where 



p = density of water 

 £ = specific heat of water 

 V = volume of water body 

 K = net surface heat exchange coefficient 

 A = surface area 

 Tg = equilibrium temperature 

 H = artificial heat input 



It can be shown that the surface heat exchange scale is 



(^)? 



'iff 



(3-21) 



Since the density ratio is normally unity, this reduces to 



K, = -^ . (3-22) 



One of the peculiarities of equation (3-22) is that if (Lj^)^ = 1:1,000 

 and (Ly) = 1:100 (common scales in tidal models), then Kj. = 1.0 



Because sediment transport processes are very complex and poorly 

 understood, reliable sedimentation similitude relations cannot be 

 developed. Model simulation of sediment transport is therefore empirical 

 and depends on a trial-and-error procedure to develop an appropriate test- 

 ing technique by which to reproduce known sedimentation patterns. 



Although scale relations can be determined for various phenomena by 

 analytical means, there is still no assurance that a distorted-scale 

 model will accurately reproduce prototype-flow conditions without com- 

 paring model and prototype observations. This is the result of not being 

 able to determine the distribution of roughness (including density gradient- 

 induced mixing) throughout the prototype. Therefore, it is necessary to 

 carefully adjust the model roughness until measured prototype tides, 

 velocities, and salinities are accurately reproduced. This process is 

 referred to as model verification, 



b. Selection of Model Scales . The "ideal" scales and/or distortion 

 for the various types of studies conducted in a particular model are often 

 conflicting. For example, it has been shown analytically that the ideal 



57 



