4.3. LONG-WAVE HYDRODYNAMIC MODELS
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2. Buoyant rise of the jet if it is submerged.
3. Convective spreading of the effluent from an initial dilution
zone over the surface of the receiving water.
4. Mass transport of the effluent by ambient waves and currents.
5. Diffusion and dispersion due to wave- and current-induced
turbulence in the ambient waters.
6. Loss of heat by evaporative cooling at the surface.
All of the scaling requirements listed for short-wave models are also
valid for geometrically undistorted long-wave models. The main difficulty
in this case may be in assuring turbulent flows in an undistorted long-wave
model. However, most long-wave models are geometrically distorted, and
this impacts on our ability to conduct accurate thermal dispersion studies
in long-wave models.
Parker, et al. (1976) noted that the thermal dispersion problem can be
divided into three regions: the near field, where entrainment is important;
the joining region, where buoyancy, surface cooling and convection are important (along with entrainment); and the far field, where surface cooling,
convection, and dispersion are important. Parker, et al. (1976) compared
prototype measurements to predictions from a distorted hydraulic model
that modeled all three regions simultaneously, and they concluded that
geometric distortion influenced model results.
Jet Diffusion. At the point of discharge of the heated water into the surrounding water, the inertia of the jet and the turbulent entrainment of cool
water are important. Similitude of this process requires geometric similarity, flow scaled according to the Froude criterion, and an outfall Reynolds
number above a value of 5000 (Lavender and Cowley 1975). Geometrically
distorted hydraulic models do not fulfill these similitude requirements, thus
we should expect that the physical processes associated with the discharge
jet will not be modeled correctly.
Parker, et al. (1976) compared measurements from a prototype installation on the James River to results from a distorted hydraulic model having a
horizontal scale of Nx = 1000 and a vertical scale of Nz = 100 (a distortion
of 10). Field data indicated that entrainment was not properly modeled in
the near field and in the joining region because the heat dissipation in the
field was higher than model predictions, indicating that model entrainment
was low.
157
2. Buoyant rise of the jet if it is submerged.
3. Convective spreading of the effluent from an initial dilution
zone over the surface of the receiving water.
4. Mass transport of the effluent by ambient waves and currents.
5. Diffusion and dispersion due to wave- and current-induced
turbulence in the ambient waters.
6. Loss of heat by evaporative cooling at the surface.
All of the scaling requirements listed for short-wave models are also
valid for geometrically undistorted long-wave models. The main difficulty
in this case may be in assuring turbulent flows in an undistorted long-wave
model. However, most long-wave models are geometrically distorted, and
this impacts on our ability to conduct accurate thermal dispersion studies
in long-wave models.
Parker, et al. (1976) noted that the thermal dispersion problem can be
divided into three regions: the near field, where entrainment is important;
the joining region, where buoyancy, surface cooling and convection are important (along with entrainment); and the far field, where surface cooling,
convection, and dispersion are important. Parker, et al. (1976) compared
prototype measurements to predictions from a distorted hydraulic model
that modeled all three regions simultaneously, and they concluded that
geometric distortion influenced model results.
Jet Diffusion. At the point of discharge of the heated water into the surrounding water, the inertia of the jet and the turbulent entrainment of cool
water are important. Similitude of this process requires geometric similarity, flow scaled according to the Froude criterion, and an outfall Reynolds
number above a value of 5000 (Lavender and Cowley 1975). Geometrically
distorted hydraulic models do not fulfill these similitude requirements, thus
we should expect that the physical processes associated with the discharge
jet will not be modeled correctly.
Parker, et al. (1976) compared measurements from a prototype installation on the James River to results from a distorted hydraulic model having a
horizontal scale of Nx = 1000 and a vertical scale of Nz = 100 (a distortion
of 10). Field data indicated that entrainment was not properly modeled in
the near field and in the joining region because the heat dissipation in the
field was higher than model predictions, indicating that model entrainment
was low.