Notice that the units of density are kg/ m 3. Similarly define the expression for the density (den) as shown below: If you want to change any thing, you can edit it and click on apply to redefine your expression. In the second half you see the definition of expression for viscosity. In above half the expression name is shown along with the value and units. Now the dialogue box for vis expression will look as follows: You will notice that the units are changed to italic fonts, which is indication that entered units are acceptable by CFX syntax. So type Pa (P in capital letters and a in small letters, as defined by CFX internal working) and press space-bar and type s (small letter). In SI system, units of viscosity *we are talking about dynamics viscosity) are Pa.S (or N s/m 2). Inside square bracket put units for viscosity in SI units. In second half of above dialogue box (Details of vis), type the value of vis as 0.002, press space-bar and put square bracket. This will open a new dialogue box for entering expression details. Put name as vis (shortcut for viscosity) and click on OK. This will open a dialouge box and put the name for expression. And then go to Expressions, Functions and Variables and then right click on Expressions and click on insert to insert new expression. In order to define expression, go to tree outline.
This is part of online course at udemy CFD course These material properties will be used to define the new custom material. Here I am giving one example of using expression to create expressions for density and viscosity. Here I have placed the some common variables with units, taken from CFX-Pre user guide. This is part of airfoil simulation in CFX (cfx file can be provided on request) Similar drag and lift coefficients are defined from X and Y component of force receptively. Velocity in x and y direction are set as Uinf times the cos and sin components respectively. They are created from variables and also from other expressions. Here I have created expressions for different requirements. For power use ^ sign and -ve sign for the unit in denominator. In CEL, you must enclose units in square brackets, and give space between two units. For example velocity has units of meter per second. Values can be dimensional or non dimensional. Drag coefficientĬEL can be used to define values and expressions. Defining an expression for evaluation of derived variable in CFD Post, e.g.Define material properties that depend on other variables.It is based on CFX expression language (CEL). CEL can be used to:
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