Fluid Mechanics CFD Simulation

What is Fluid Mechanics?

In fluid mechanics, the behavior of fluids at rest and in motion, as well as the reasons for these behaviors, are studied. A sufficient understanding of fluid mechanics helps scientists and engineers in fields such as thermodynamics and heat transfer. Additionally, the design of any system involving a fluid, from batteries with liquid electrolytes to motorcycles moving through the air, requires knowledge of fluid mechanics.

 

Key Concepts in Fluid Mechanics

In the following, we discuss important concepts in fluid mechanics that are used to classify fluid phenomena:

• Static or dynamic fluid: If the fluid does not move, it is in a static state. If the velocity of the fluid is not zero, it is in a dynamic state.
• Steady or transient flow: If the parameters of the fluid flow, including speed and pressure at any point, do not change with respect to time, the flow is steady; otherwise, it is transient. In steady flow, the derivative of each parameter relative to time at any point is zero.
• Flow regime: Fluid flow can be laminar or turbulent. The flow regime affects the velocity and pressure distribution in the flow, resulting in fluid phenomena such as boundary layers and pressure drops being functions of the flow regime. To investigate any fluid phenomenon, it is necessary to determine its flow regime first.
• Fluid viscosity: Historically, for the analytical solution of fluid problems, it was initially assumed that the viscosity of the fluid is zero, or inviscid. Surprisingly, despite this assumption, many engineering achievements were made, and this assumption is still used in some problems today. However, for accurate solutions and many applications in fluid mechanics, viscous fluid is considered. There are different models for fluid viscosity, and one of the challenges in simulations and analytical problems is selecting the appropriate viscosity model for the fluid. In some cases, viscosity changes with temperature, pressure, and even time, posing significant challenges for engineers.
• Compressible and incompressible fluid: If the density of a fluid changes with pressure, the fluid is considered compressible; otherwise, it is incompressible. Usually, all fluids experience slight changes in density with pressure changes. Whether a fluid is assumed to be compressible or incompressible depends on the context and the level of precision required by the engineer or scientist.
• Compressible and incompressible flow: In fluid mechanics, it is typically mentioned that if the flow speed is greater than 0.3 times the speed of sound in the fluid, the flow is considered compressible; otherwise, it is incompressible. In incompressible flow, a compressible fluid can be assumed to be incompressible.
• Newtonian and non-Newtonian fluid: If the viscosity of a fluid changes with factors such as temperature, pressure, range of motion, speed, or time, then the fluid is non-Newtonian. Conversely, if the viscosity remains constant regardless of these factors, the fluid is Newtonian. Ketchup and blood are examples of non-Newtonian fluids, while air and water are examples of Newtonian fluids.
• Ultrasonic, subsonic, and sonic flow: If the flow speed is lower than the speed of sound, it is subsonic flow; if it is equal to the speed of sound, it is sonic flow; and if it is higher, it is supersonic flow. Each of these regimes has its own equations. Whether experimentally, analytically, or through simulations, supersonic flow presents a significant challenge for engineers. Supersonic flow is commonly encountered in aerospace applications.

 

Fluid Mechanics Applications

Wherever there is fluid, fluid mechanics is used. Some applications include:

• Aeronautics and aerospace engineering: In aerospace engineering, the critical task involves analyzing fluid movement around objects and their interactions. Airfoil and airplane wing design, as well as airplane control and propulsion systems, are closely related to fluid mechanics. CFD fluid mechanics simulations are widely used to predict aerodynamic performance and optimize designs.
• Civil engineering: In civil engineering, several critical tasks must be managed during building construction. These include pumping liquid concrete to significant heights, constructing water and sewage facilities, and ensuring that wind does not cause vibrations or unwanted noise when interacting with the building. These aspects are essential for the structural integrity, functionality, and comfort of the building once completed. CFD fluid mechanics simulations help in designing HVAC systems and assessing wind loads on structures.
• Biomedical engineering: The study of how blood and fluids move within the body falls under the umbrella of fluid mechanics. This field helps in designing artificial parts of the body, such as artificial heart valves. It also explores methods of drug delivery, studies the movement of micro-particles, and investigates reasons for fat deposition in veins. CFD simulations aid in optimizing blood flow patterns and analyzing drug dispersion in the body.

Artificial heart valves, designed based on fluid mechanics rules

 

• Marine engineering: Fluid mechanics plays a crucial role in the design of marine structures such as oil rigs, ships, and submarines. CFD simulations are widely used in marine engineering.

Fluid mechanics is integral to submarine design, influencing aspects such as propulsion through water, maneuvering, and controlling depth.

 

• Mechanical engineering: The design and utilization of pumps, compressors, turbines, heat exchangers, hydraulic systems, and more are integral subsets of mechanical engineering. Each of these technologies relies heavily on principles from fluid mechanics to function effectively. CFD simulations are essential for optimizing the performance and efficiency of these devices across various applications.

 

Simulation of Fluid Mechanics by ANSYS Fluent

The basis of ANSYS Fluent software is to simulate fluid mechanics processes. This software is capable of simulating all fluid phenomena. In terms of CFD simulation methods and algorithms, Fluent has demonstrated extraordinary performance by employing the finite volume method. The software offers various models to simulate turbulent flow regimes and different viscosity models. Users can choose their preferred simulation algorithm and customize its settings in detail. CFD in fluid mechanics enables precise simulation and analysis of fluid behavior, enhancing the design and optimization of various engineering systems.

Velocity magnitude contour, simulated by ANSYS Fluent, from “External Gear Pump CFD Simulation Using Dynamic Mesh”

 

CFDLAND expertise in Fluid Mechanics Modeling Using ANSYS Fluent Software

At CFDLAND, our specialists are highly skilled and experienced in simulating fluid mechanics phenomena. Whether you need simulations for the Magnus effect, boundary layer separation, or any other fluid-related project, you can trust us to deliver excellent results. Place your order for a CFD simulation project at ORDER PROJECT.

You can view the simulation projects we have completed with ANSYS Fluent on CFD SHOP. Additionally, our projects in the field of fluid mechanics can be found at the top of this page. Delve into them; you might find a project that interests you.