Fluid Simulation is not working when a object is used as fluid obstacle I am trying to simulate the fluid in a pipe. The fluid obstacle object (pipe) is converted to mesh from a path. I have set a fluid inflow at one end of the pipe and fluid outflow at one end of the pipe. When I try to bake the fluid domain it stays as a cube and nothing happens.

Just as a test, I created a simple pipe (converted to mesh from a path) in another file and tried to flow the fluid through the pipe, it was quite slow and sluggish as compared to the simple pipe extruded from a cube.

Is the failure in the fluid simulation is due to more complexity of the obstacle object or some problem with setting of fluid objects?
Aside from making the resolution high, you would need to subdivide the fluid, and increase the fluid speed and duration to match your animation. I.e. if you are running a 500 frame animation at 50fps, set the fluid time: (1 to 500/50). This will match the fluid speed to your animation so that it doesn't go slower than normal. Lastly, if you don't have the computer memory to run the sim at a high resolution, scale up the objects while keeping the domain at the smallest you can. It needs to be bigger than the fluid objects, though.