Introduction

Computational fluid dynamics ( CFD) is a branch of fluid mechanics that analyzes and solves problems involving fluid flows using numerical analysis and data structures. CFD applies to a broad variety of research and engineering problems in many fields of study and industry including aerodynamics and aerospace analysis, weather modeling, natural science and environmental engineering, design and analysis of industrial structures, biological engineering, fluid flow, and heat transfer, and engine and combustion analysis.

CFD simulations considered are performed in a steady-state for laminar and turbulent flows, given that the fluid is viscous, incompressible and monophasic, and that the fluid movement is an isothermal mechanism (without transfer of heat).

External flows past objects have been studied extensively because of their many practical applications. For example, airfoils are made into streamline shapes in order to increase the lifts, and at the same time, reducing the aerodynamic drags exerted on the wings. On the other hand, flow past a blunt body, such as a circular cylinder, usually experiences boundary layer separation and very strong flow oscillations in the wake region behind the body. In certain Reynolds number range, a periodic flow motion will develop in the wake as a result of boundary layer vortice being shed alternatively from either side of the cylinder. This regular pattern of vortices in the wake is called a Karman vortex street. It creates an oscillating flow at a discrete frequency that is correlated to the Reynolds number of the flow. The periodic nature of the vortex shedding phenomenon can sometimes lead to unwanted structural vibrations, especially when the shedding frequency matches one of the resonant frequencies of the structure.

Dimensions of pipe:

Diameter - 30mm

Length - 0.05m

Calculation of velocity:

Fluid: Hydrogen

Increase the Reynolds number by a factor:

Here the baseline simulation Re= 2100(concidering)

calculation of velocity:

Re*mu/D*rho = U_inlet

• D = cylinder diameter
• mu = dynamic viscosity
• rho = density

Concidering: Time dependency simulation.

• If the inlet velocity is 10.647887323944 m/s and if the length of the domain is 2 m then the flow through time is 0.1878 seconds.
• This 0.1878 second is called the flow through time.
• The end time would be 0.450794 seconds.

Case	Flow type	Factor(%)	Reynolds Number (Re)	viscosity (μ)(N-s/m^2)	Diameter (D)(m)	density(ρ)(Kg/m^3)	Velocity(m/s)	Length of the domain(m)	Flow through time (sec){L/V}	End time (sec)
1	laminar	0	2100	0.009	0.03	71	8.873239437	2	0.225396825	0.450794
2	transient	20	2520	0.009	0.03	71	10.64788732	2	0.187830688	0.375661
3	transient	40	2940	0.009	0.03	71	12.42253521	2	0.160997732	0.321995
4	turbulent	100	4200	0.009	0.03	71	17.74647887	2	0.112698413	0.225397

PROCEDURE FOR DOING FLOW OVER A CYLINDER SIMULATION IN SOLID WORKS

Step 1: Creating the cad model for the pipe(circle for diameter of pipe - extrude). And save the part.

Step 2: Click flow simulation and wizard.

1. Project name
2. Unit system- default.
3. Analysis type - external - Time dependent as considered above.
4. Default fluid - selection of fluid.
5. Wall condition.
6. Initial & ambient condition - creating velocity direction based on model and its value .

Step 3: now we can edit the computational domain.

Step 4: Now create the mesh using manual option and define the number as our wish.(Higher mesh cube inside part gives more accurate rate)

Step 5: Now run the basic simulation.

Step 6: Now click on results and make the cut plot at where we neede to see how the property of fluid is at that area or section.

Step 7: Now click on animation and interpolate the flow.

Step 8: We can save the results.

General settings:

case1:

case 2:

case 3:

case 4:

result video link: https://youtu.be/fZOJnRIBVig

Conclusion:

We can see the different cases pressure and velocity induced around the cylinder.

we can see high pressure around the surface and the velocity is minimum in that area.

Case	Pressure max(Pa)	Pressure min(Pa)	velocity max(m/s)	velocity min(m/s)
1	101327.85	101.322.69	10.377	0.679
2	101329.12	101321.72	12.702	0.788
3	101330.55	101320.53	14.565	0.922
4	101336.44	101315.65	20.887	1.311

so we can see the increasing order of plot max and decreasing order of plot in which infer the change in velocity reults in increase of velocity and where the velocity is low pressure is induced more in thatregion.

Reference:

https://study.com/academy/lesson/reynolds-number-definition-equation.html#:~:text=The%20Reynolds%20number%20is%20a%20dimensionless%20value%20that%20is%20used,moves%20smoothly%20and%20is%20predictable.

https://www.ajdesigner.com/reynoldsnumber/reynoldsv.php#ajscroll