Flow over a cylinder

AIM -

To perform a baseline solidwork flow simulation over a solid cylinder at different velocities.

OBJECTIVE -

Design a cylinder model in solidwork and run a flow simulation over it.

Compare the results obtained in various cases.

Create the animation of velocity and pressure at each cases.

INTRODUCTION -

Flow Simulation enables users to simulate a wide variety of liquids and gases for different engineering scenarios. A few common applications are flow through manifolds, heat exchangers, electronics cooling and aerodynamics. External flow simulation around a product is important to understand its aerodynamic characteristics and the pressure distribution induced by the fluid on it.

Reynolds number -

Reynold number is a ratio of inertia force to viscous force. It is the key parameter in determining whether or not a flow is laminar or turbulent.

Reynolds number is a non-dimensional number consisting of velocity scale and length scale. It's a product of velocity scale and length scale over kinematic viscosity.For external flow, the Reynolds number is based on the freestream velocity and the characteristic size if the object over which it flows.The Reynolds number for turbulent flow over a body or so called external flow is similar to what was mentioned above but the flow being turbulent in nature.

CASE SETUP -

So, here we have performed the flow simulation over a cylinder by using different velocities. But these velocities where found through the reynolds number which was calculated by taking the factors of 20% , 40% , 100% to a fixed reynolds number. Here ,first of all with initial velocity value 10 (m/s) we found the reynold number. Through these reynold number we mutliplied it with the factor of 20% , 40% , 100% . Know we have the value of reynolds number so futher we calcuated the velocities for each of these three values i.e., at 20% , 40% , 100%.

The other parameters required for calculation like density, diameter of cylinder, dynamic viscosity (at 18 degree) were taken standard.

Below are the details of Inputs , Reynold number at each cases and velocities.

Now since the input parameters are there reynold number is calculated.

Above we have calculated the values at 20%, 40%, 100% . Using these reynold number we futher calculate the velocity at each of these three reynold number.

These the values of velocities are given below-

So, finally we have three values of velocity -

At 20% of reynold number i.e., Re = 32307.6 the velocity is 12 (m/s).

At 40% of reynold number i.e., Re = 37692.2 the velocity is 14 (m/s).

At 100% of reynold number i.e., Re = 53846 the velocity is 20 (m/s).

Now, initally we have the theoretical setup ready so next we need is a cylinder model and we need to import it in flow simulation of SOLIDWORK.

Above is the cad model required for the flow simulation.

The diameter for the cylinder is 40mm and it is extruded to 50mm in length. So, the cad model we ready and we need to proceed next step that is flow simulation.

Since, we are having the external flow simulation and that with time dependant so we need to calcuate the simulation end time.

SIMULATION SETUP -

Simulation end time calculation -

Here the time is considered to be 2 secs. So total analysis time input in simulation wizard is given as 2 sec. So , now i want 10 output results then i need to calculate the total analysis time by my total output number i.e., 2/10 = 0.2 . Finally, 0.2 sec will be the output time step.

The fluid is taken as air and according to the velocity value we have given the input velocity through X direction of cylinder so that the velocity can flow over the cylinder.

Now we have three cases i.e., velocity at 12(m/s) , 14(m/s) and 20(m/s)

CASE 1 - Velocity at 12 (m/s)

We perform this case at velocity value 12 m/s and found the velocity and pressure plot along with the animation .

Cut plot of velocity -

The cutplot of velocity above gives us the discretization of velocity over the cylinder as shown in diagram. Here we can compute that the least velocity in computational domain over a cylinder is 4.1 m/s and maximum is 15.57 m/s. We can conclude that the since the input velocity was 12m/s the flow of velocity has reached maximum to 15.57 m/s.

Cut plot of pressure -

The cutplot of pressure above gives us the discretization of pressure over the cylinder as shown in diagram. Here we can compute that the least pressure in computational domain over a cylinder is 101277.23 Pa and maximum is 101394.42 Pa. We can conclude that there is not any pratical evolution of the pressure but is still little at the impact of velocity to the cylinder and as it leaves it, it goes decreasing.

CASE 2 - Velocity at 14 (m/s)

We perform this case at velocity value 14 m/s and found the velocity and pressure plot along with the animation .

Cut plot of velocity -

The cutplot of velocity above gives us the discretization of velocity over the cylinder as shown in diagram. Here we can compute that the least velocity in computational domain over a cylinder is 5.3 m/s and maximum is 18.4 m/s. We can conclude that the since the input velocity was 14m/s the flow of velocity has reached maximum to 17.92 m/s.

Cut plot of pressure -

The cutplot of pressure above gives us the discretization of pressure over the cylinder as shown in diagram. Here we can compute that the least pressure in computational domain over a cylinder is 101301.23 Pa and maximum is 101441.42 Pa. We can conclude that there is not any pratical evolution of the pressure but is still little at the impact of velocity to the cylinder and as it leaves it, it goes decreasing.

CASE 3 - Velocity at 20 (m/s)

We perform this case at velocity value 20 m/s and found the velocity and pressure plot along with the animation .

Cut plot of velocity -

The cutplot of velocity above gives us the discretization of velocity over the cylinder as shown in diagram. Here we can compute that the least velocity in computational domain over a cylinder is 8.7 m/s and maximum is 26.1 m/s. We can conclude that the since the input velocity was 20m/s the flow of velocity has reached maximum to 26.17 m/s. Here if we look at the plot when the velocity initally flow through the cylinder its impact in point of velocity is large than we it moves forward . This happens because the reynold number is high for this velocity.

Cut plot of pressure -

The cutplot of pressure above gives us the discretization of pressure over the cylinder as shown in diagram. Here we can compute that the least pressure in computational domain over a cylinder is 101191.58 Pa and maximum is 101518.28 Pa. We can conclude that there is not any pratical evolution of the pressure but is still little at the impact of velocity to the cylinder and as it leaves it, it goes decreasing.

The link for the animation of pressure and velocity is provided below -

https://drive.google.com/drive/folders/1qR2c8vhC4xuoHWW2P_Zw0XTpy7hXf4mn

CONCLUSION -

Here, from the above case study and performing the baseline simulation over a cylinder we conclude that the increase in reynolds number increases the velocities as the reynold number is directly proportional to velocity. Using these method the above baseline simulation can also be performed for many other industrial applications.