(Fluid Mechanics) stream function graph

In summary: The curves should look like a series of cardioids, which are heart-shaped curves. In summary, the speaker is trying to draw the streamlines of the given stream function and is unsure if it should be treated as a normal function or a polar plot. They have tried plotting it using polars and keeping r constant, but are not sure if it is correct. They suggest plotting ##\Psi(r,\theta)=C=\mathrm{constant}## for different values of C to get a series of cardioid curves.
  • #1
DoctorCasa
1
0
Hello, I got this stream function
ψ(r,θ)=sqrt(r)*sin(θ/2)

I have to draw the streamlines of this fuction, however, I'm not sure how to afford this, should I consider this just like a normal function that depends on tetha and rho, or it's more like a polar plot?

When i drew the streamlines using polars, I got a family of cardioids(heart-like graph). When I plotted this on matlab, keeping r constant, I got a sin, which it's pretty obvious, but I don't think that's correct.

What do you guys think?
 
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  • #2
DoctorCasa said:
Hello, I got this stream function
ψ(r,θ)=sqrt(r)*sin(θ/2)

I have to draw the streamlines of this fuction, however, I'm not sure how to afford this, should I consider this just like a normal function that depends on tetha and rho, or it's more like a polar plot?

When i drew the streamlines using polars, I got a family of cardioids(heart-like graph). When I plotted this on matlab, keeping r constant, I got a sin, which it's pretty obvious, but I don't think that's correct.

What do you guys think?

I think you are supposed to plot ##\Psi(r,\theta)=C=\mathrm{constant}## for different values of C. For each value you will get a curve in the x-y plane.
 

1. What is a stream function graph?

A stream function graph is a graphical representation of fluid flow in a two-dimensional plane. It is a contour plot where the value of the stream function at any point represents the flow rate at that point. The stream function is a mathematical function that helps describe the motion of a fluid.

2. How is a stream function graph useful in fluid mechanics?

A stream function graph is useful in fluid mechanics because it allows us to visualize the flow patterns of a fluid. By analyzing the streamlines on the graph, we can determine important properties of the flow such as velocity, direction, and vorticity. This information is crucial in understanding and predicting the behavior of fluids in various systems.

3. How is a stream function graph different from a velocity vector field?

A stream function graph and a velocity vector field are two different ways of representing fluid flow. While a velocity vector field shows the magnitude and direction of the velocity at each point in the fluid, a stream function graph shows the flow rate at each point. Additionally, a stream function graph is only applicable for two-dimensional flows, while a velocity vector field can be used for both two and three-dimensional flows.

4. Can a stream function graph be used for compressible fluids?

No, a stream function graph is only applicable for incompressible fluids. In compressible fluids, changes in density can affect the flow rate and therefore, the stream function. As a result, the stream function cannot accurately represent the flow in these cases.

5. How can a stream function graph be used to solve fluid mechanics problems?

A stream function graph can be used to solve fluid mechanics problems by helping us understand and visualize the flow patterns in a system. By analyzing the streamlines and calculating the stream function at different points, we can determine important properties such as pressure, velocity, and vorticity. This information can then be used to solve equations and equations of motion to predict the behavior of the fluid in the system.

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