Flow Simulation over Cylinder using Solidworks Flow Simulation
OBJECTIVE:
To perform flow simulation over a cylinder with various different inlet velocity corresponding to their Reynolds number using Solidworks Flow Simulation and conclude the result.
ABSTRACT:
The project purpose was to perform flow motion analysis over a cylinder having air as a fluid using SolidWorks Flow Simulaion. Here, the fluid has different values of Reynolds Number at inlet. The first value of Reynold number is to be calculated from the formula and the rest three have to be increased by a factor of 20%, 40% & 100% separately. Generate velocity profiles and animations for pressure-velocity for all the four Reynolds number. Further, for all Reynolds number value, profiles & animations were compared and a conclusion was made from the analysis results.
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CONTENTS:
1. Introduction
- Computational Fluid Dynamics (CFD)
- Reynolds Number (Re)
- Velocity Profile
2. Geometry Model
3. Flow Motion Analysis
- Case 1: Inlet Flow Velocity is 10 m/s
- Setup
- Boundary Condition
- Mesh Parameter
- Result (Velocity profile & animation)
- Case 2: Reynolds number increased by 20%
- Setup
- Boundary Condition
- Mesh Parameter
- Result (Velocity profile & animation)
- Case 3: Reynolds number increased by 40%
- Setup
- Boundary Condition
- Mesh Parameter
- Result (Velocity profile & animation)
- Case 4: Reynolds number increased by 100%
- Setup
- Boundary Condition
- Mesh Parameter
- Result (Velocity profile & animation)
4. Observation
5. Conclusion
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1. INTRODUCTION:
Computational Fluid Dynamics (CFD)
Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical analysis and data structures to analyse and solve problems that involve fluid flows. Computers are used to perform the calculations required to simulate the free-stream flow of the fluid, and the interaction of the fluid (liquids and gases) with surfaces defined by boundary conditions. With high-speed supercomputers, better solutions can be achieved, and are often required to solve the largest and most complex problems.
CFD is applied to a wide range of research and engineering problems in many fields of study and industries, including aerodynamics and aerospace analysis, weather simulation, natural science and environmental engineering, industrial system design and analysis, biological engineering, fluid flows and heat transfer, and engine and combustion analysis.
Reynolds Number (Re)
The Reynolds number (Re) is an important dimensionless quantity in fluid mechanics used to help predict flow patterns in different fluid flow situations. At low Reynolds numbers, flows tend to be dominated by laminar (sheet-like) flow, while at high Reynolds numbers turbulence results from differences in the fluid's speed and direction, which may sometimes intersect or even move counter to the overall direction of the flow (eddy currents).
The Reynolds number is the ratio of inertial forces to viscous forces within a fluid which is subjected to relative internal movement due to different fluid velocities. A region where these forces change behaviour is known as a boundary layer, such as the bounding surface in the interior of a pipe.
With respect to laminar and turbulent flow regimes:
- laminar flow occurs at low Reynolds numbers, where viscous forces are dominant, and is characterized by smooth, constant fluid motion;
- turbulent flow occurs at high Reynolds numbers and is dominated by inertial forces, which tend to produce chaotic eddies, vortices and other flow instabilities.
The Reynolds number is defined as:
where:
ρ is the density of the fluid (SI units: kg/m3)
u is the flow speed (m/s)
D is the diameter of the tube (m)
μ is the dynamic viscosity of the fluid (Pa·s or N·s/m2 or kg/(m·s))
ν is the kinematic viscosity of the fluid (m2/s).
From the above formula, velocity at a particular Reynold Number can be calculated by putting the values for air as ρ = 1.225 kg/m3, D = 0.02 m, μ = 1.81 * 10-5 kg/(m-s) & ν = 1.48 * 10-5 m2/s
For case 1, Flow Speed (u) = 10 m/s Reynold Number (Re) = 13,536
For case 2, Reynold Number (Re) = 16,243.2 Flow Speed (u) = 12 m/s
For case 3, Reynold Number (Re) = 18,950.4 Flow Speed (u) = 14 m/s
For case 4, Reynold Number (Re) = 27,072 Flow Speed (u) = 20 m/s
Velocity Profile
A pictorial graph of the speed of a fluid flow as a function of distance perpendicular to the direction of flow.
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2. GEOMETRY MODEL
Cylinder Diameter: 20 mm
Cylinder Length: 50 mm
Material Assigned: AISI 1015 Steel, Cold Drawn (SS)
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3. FLOW MOTION ANALYSIS
- Case 1: Inlet Flow Velocity is 10 m/s
1) Setup
- Project name: Flow_at_10
- Analysis type: External
- Type of fluid: Air
- Type of flow: Laminar & Turbulent
- Wall Condition: Adiabatic Wall with 0 micro-meter roughness
- Initial Condition: Pressure (101325 Pa), Temperature (293.2K), Velocity x-direction (10 m/s)
- Computational Domain length in x-axis is 500 mm and in y-axis is 300 mm.
Calculation of simulation time using Inlet Velocity and the Computational Domain Length-
Time = Distance / Speed
Inlet Velocity = 10 m/s
Computational Domain Length in x-axis = 0.5 m
Time = 0.05 s
Since, the simulation time should be twice the calculated time.
Therefore, Simulation Time = 0.1 s & time step = 0.01 s
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2) Boundary Condition
Wall Boundary Condition: Inner face of pipe/shell (Real Wall)
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3) Mesh Parameter
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4) Result (Setting cut plot & animation)
Cut plot parallel to the circular cross-section of the cylinder and at the mid length.
- Velocity Profile
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- Pressure Profile
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- Simulation for Velocity Profile
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- Simulation for Pressure Profile
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- Case 2: Reynolds number increased by 20%
1) Setup
- Project name: Flow_at_12
- Analysis type: External
- Type of fluid: Air
- Type of flow: Laminar & Turbulent
- Wall Condition: Adiabatic Wall with 0 micro-meter roughness
- Initial Condition: Pressure (101325 Pa), Temperature (293.2K), Velocity x-direction (12 m/s)
- Computational Domain length in x-axis is 500 mm and in y-axis is 300 mm.
Calculation of simulation time using Inlet Velocity and the Computational Domain Length-
Time = Distance / Speed
Inlet Velocity = 12 m/s
Computational Domain Length in x-axis = 0.5 m
Time = 0.045 s
Since, the simulation time should be twice the calculated time.
Therefore, Simulation Time = 0.09 s & time step = 0.009 s
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2) Boundary Condition
Same as case 1
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3) Mesh Parameter
Same as case 1
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4) Result (Setting cut plot & animation)
Cut plot parallel to the circular cross-section of the cylinder and at the mid length.
- Velocity Profile
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- Pressure Profile
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- Simulation for Velocity Profile
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- Simulation for Pressure Profile
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- Case 3: Reynolds number increased by 40%
1) Setup
- Project name: Flow_at_14
- Analysis type: External
- Type of fluid: Air
- Type of flow: Laminar & Turbulent
- Wall Condition: Adiabatic Wall with 0 micro-meter roughness
- Initial Condition: Pressure (101325 Pa), Temperature (293.2K), Velocity x-direction (14 m/s)
- Computational Domain length in x-axis is 500 mm and in y-axis is 300 mm.
Calculation of simulation time using Inlet Velocity and the Computational Domain Length-
Time = Distance / Speed
Inlet Velocity = 14 m/s
Computational Domain Length in x-axis = 0.5 m
Time = 0.35 s
Since, the simulation time should be twice the calculated time.
Therefore, Simulation Time = 0.07 s & time step = 0.007 s
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2) Boundary Condition
Same as case 1
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3) Mesh Parameter
Same as case 1
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4) Result (Setting cut plot & animation)
Cut plot parallel to the circular cross-section of the cylinder and at the mid length.
- Velocity Profile
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- Pressure Profile
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- Simulation for Velocity Profile
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- Simulation for Pressure Profile
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- Case 4: Reynolds number increased by 100%
1) Setup
- Project name: Flow_at_20
- Analysis type: External
- Type of fluid: Air
- Type of flow: Laminar & Turbulent
- Wall Condition: Adiabatic Wall with 0 micro-meter roughness
- Initial Condition: Pressure (101325 Pa), Temperature (293.2K), Velocity x-direction (20 m/s)
- Computational Domain length in x-axis is 500 mm and in y-axis is 300 mm.
Calculation of simulation time using Inlet Velocity and the Computational Domain Length-
Time = Distance / Speed
Inlet Velocity = 20 m/s
Computational Domain Length in x-axis = 0.5 m
Time = 0.025 s
Since, the simulation time should be twice the calculated time.
Therefore, Simulation Time = 0.05 s & time step = 0.005 s
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2) Boundary Condition
Same as case 1
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3) Mesh Parameter
Same as case 1
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4) Result (Setting cut plot & animation)
Cut plot parallel to the circular cross-section of the cylinder and at the mid length.
- Velocity Profile
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- Pressure Profile
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- Simulation for Velocity Profile
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- Simulation for Pressure Profile
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4. OBSERVATION:
From the above contours, an observation table was created.
From the above table, the following observation can be made-
- For each Reynolds number, the maximum air velocity can be observed on the portion of leading face and the minimum air velocity on the front quarter point & trailing or back face of the cylinder.
- For each case, the front quarter point of the circular cross-section is the stagnation point (point where the velocity is zero) and experiences the maximum pressure & minimum velocity.
- On increasing the Reynolds number, the inlet velocity also increases.
- From all the 4 cases, the maximum velocity & pressure is experienced in the case of the flow with the highest Reynolds number.
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5. CONCLUSION:
The flow simulation analysis helps to analyse the maximum & minimum regions of velocity & pressure over the cylinder with different inlet velocities.
The highest the Reynolds number, the higher will be the velocity & pressure experience over the geometry.
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