User Guide 003

Hydrodynamics

The hydrodynamic parameters are divided into different groups: Water Properties, Bottom Friction, Wall Friction, Eddy Viscosity, Wave Mass Flux, and Wind and Atmospheric Pressure. Each group is discussed in detail in the following sections. A brief over is provided on what the options and parameters are, where to change them and other pertinent information.

figure 2-23

Water Properties

The properties of sea water are a function of temperature, salinity (i.e. dissolved minerals) and pressure. The water density and dynamic viscosity (kinematic viscosity times the water density) are shown in the following two figures as a function of water temperature and salinity.

figure 2-24 figure 2-25

CMS uses the water density and viscosity in various hydrodynamic and sediment transport calculations. The water density and viscosity are as-sumed to be constant and can be either user-specified or calculated inter-nally based on the water temperature and salinity. The water temperature must always be specified, while either the water density or salinity need to be specified. If the salinity is not specified, then it is calculated from the water density. The salinity value used to calculate the water density and viscosity are independent of the salinity transport (initial condition and time-varying solution). Below is a table describing the CMS cards related to the specification of the water properties.

table 2-23

In SMS 11.1 and earlier versions, only the option to specify the water density and temperature were available (see Figure 2 23). Below is an example of the CMS cards used to specify the water density and temperature are specified as when using the SMS interface. The default salinity value of 35 ppt is used to estimate the water viscosity. Therefore, if the user wishes to simulate a fresh water location, the salinity should also be modified.

Example 2-8

If the user wants the model to calculate the water density based on the water temperature and salinity, or to change the default salinity value used in the water density and viscosity calculations, then the user must manually edit the CMS-Flow Control File. Below is an example where the Card file is manually modified (advanced) and the water temperature and salinity specified.

example 2-9

Notes: 1. CMS uses a constant density, and kinematic viscosity. The water density and kinematic viscosity can be either specified are calculated based on the water temperature and salinity. The salinity value used in the water properties section is independent of the salinity transport initial condition and solution. 2. The kinematic viscosity and water density y are used in the many of the sediment transport calculations. 3. The water properties are NOT calibration parameters and should be estimated as best as possible. 4. All water properties are written in the CMS_Diag.txt file for the user’s reference.