Drag and Coefficent of Drag in Cosmosfloworks

Hi For one of my projects, I need to test various shapes and designs in order to caculate Drag and Coefficent of drag. I see an option in Fluent such as Monitor -> Forces Cd(coeff of drag), but I do not see any options like this in cosmosfloworks. Please tell me if one in avaliable in cosmosworks, and if not, any alternatives.

Thanks for all the help. James :)

Reply to
jameszhao00
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James

I have done this by taking the reaction force in what ever direction you want the drag in and then putting in a 'equation goal' (look this up in the cosmos help) using the formula

D = Cd * 1/2 * rho * v^2 * S where rho is the density of air, v is the velocity of the fluid, D is the drag force and S is the cross sectional area seen perpendicular from the direction of flow. So you will need to rearrange this to get Cd, so you have

Cd = (1/2 rho V^2 S)/D

From cosmos you get D (set it up as a goal and give it a variable name) next you need to know the cross sectional area (calculated using split lines and a surface, density of the air and the velocity of the fluid

Punch all this into a equation goal and Viola! It will spit it out into a spreadsheet nicely.

I cannot send any examples unfortunately as I no longer work at a place that has a Flow license. This is just from memory. So double check the formula but I am pretty sure that is it

Ben

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Reply to
Ben Eadie

Thanks for your help. James

Reply to
jameszhao00

One problem.

I think the cross-sectional area assumes a uniform shape. However, this is an arbitary shape (actually a glider) which is composed of solids with no 1 cross section.

Thank you. James

Reply to
jameszhao00

It still has a projected area you can use. Remember this is only going to give you a ball park figure, there are many considerations to take into account. For an aircraft you will most likely need to include parasitic drag, deal with the full surface area of the wind sections to develop the figure more accurately, surface finishes....etc etc. oh and have one hell of a computer to do the calculations.

If you and your company want some help, I could go into this much much further but the time involved will be too much to do over a news group or via emails.

Here is my pride and joy of work in aerodynamics we have this recumbent bike down to a min of drag the same effort that takes you to 15 KPH on a mountain bike will get you to 52 KPH on this one...We hope to break a world record in a month.

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Also I have done extensive work on this aircrafts' aerodynamics and structural analysis. and worked on some gliders in the Czech Republic when I worked there.

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You can contact me at
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find the email and phone number in the contact link

Best Regards. Ben

Reply to
Ben Eadie

Ben,

You were typing faster than you were thinking and inverted the equation. Cd=D/(1/2 rho V^2 S).

Jerry Steiger Tripod Data Systems "take the garbage out, dear"

Reply to
Jerry Steiger

Gahhh! Thanks Jerry, hope this does not mean I am garbage and you just took me out.... he he Love the signature

Ben

Jerry Steiger wrote:

Reply to
Ben Eadie

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