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Old   April 27, 2000, 10:13
Default about gravitation
  #1
Wason
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Hi all,

When I simulate the flow field of water pass a 2D large pipe,I used gravitation equal to -9.8(y direction) and the others were nornally set as air flow, but the contours of pressure apparently didn't include the effection gravitation? what's wrong with me? What should I do when I consider the gravitation in 2d/3d problem?

thanks

Wason

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Old   April 27, 2000, 11:02
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John C. Chien
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(1). Look at your y-momentum equation, you should have the body force term there. (2). If you set the inlet velocity to nearly zero, then the left-hand side convection terms and the right-hand side diffusion terms will be very small. In this case, the pressure distribution in the y-direction will be rho*g*h (dpdy=rho*g, so after integration, it gives p-p0=rho*g*h, where h=y-y0). (3). In this case, you don't need a computer or a computer program. But, if you are using someone's code, make sure that the battery is included . (sometimes, the label on the package will say that the battery is not included. In this case, the energy comes from the gravitational force term, rho*g. So, make sure that rho*g is actually included when you run the program)
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Old   April 28, 2000, 07:26
Default Re: about gravitation
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Volker Pawlik
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As far as I remember the reason wyh you don't see any gravitational effects on your solution is originated in the redefinition of the static pressure in Fluent (see. page 8-24 User'Guide Fluent 5 or better 14-67, -68 and -87 User's Guide Fluent 4). Setting the reference density rho-0 = 0 should help you with the cost of worse convergence performance.
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