Author: caesarwiratama

In fluid mechanics theory, we recognize the presence of fluid flow conditions that tend to adhere to solid walls, also known as the no-slip condition. This condition causes the velocity gradient around the surface to have specific patterns determining several parameters like shear stress, convection coefficients, and others, forming a layer with a specific thickness Read more

The shape of the control volume depends on the solver’s capabilities; structured-grid codes utilize quadrilaterals in 2D flow and hexahedrons in 3D flow. Meanwhile, unstructured grids use triangles in 2D flow and tetrahedrons in 3D flow Figure 3.2. Type of mesh In general, meshes composed of hexahedra offer advantages in terms of efficiency in the Read more

Meshing or discretization is the process of dividing the continuous fluid domain into a discrete computational domain, allowing the generally nonlinear partial differential equations of fluid mechanics to be numerically solved (further details will be discussed in the solver theory chapter). Generally, smaller mesh sizes will yield more detailed and accurate computational results but will Read more

Generally (simplified), the steps involved in the CFD process are summarized in the flowchart below: Figure 1.11. General (simplified) CFD workflow In common modern CFD packages, the geometry can be easily imported from Computer-Aided Design (CAD) software, such as Solidworks, Autodesk Inventor/Fusion 360, Catia, or an open-source modeler such as Blender with various extensions depending Read more

Generally, the fundamental problem of CFD is solving the Navier-Stokes equations. Historically, the first method developed was 2D flow around an airfoil using conformal transformation, which was developed in the 1930s. Lewis Fry Richardson used the idea of calculating using finite differences. In 1922, he divided the physical space into cells in the book Weather Read more

Because CFD solves general fluid dynamic equations (Navier-Stokes equation, or sometimes Lattice Boltzmann), it allows this program to solve complex turbulent, viscous, compressible, heat transfer, and much more; hence, the applications are also varied, ranging from aerospace, automotive, maritime, chemical process, energy generation, civil engineering, urban planning, electronics, consumer goods, bioengineering, and more. Using a Read more

In real-world applications, there’s no fluid completely free from the effects of viscosity. However, the transition from inviscid to viscous modeling in numerical CFD modeling entails significantly different computational efforts. Inviscid models are mathematically straightforward, resulting in much faster computational times. Cases that can be modeled using inviscid approaches involve very high Reynolds numbers, where Read more

For high-speed gas fluid flow (more than 0.3 speed of sound), the gas density, which is assumed to be constant in some simple modeling, can change due to significant pressure variations. The speed of sound is characterized by the Mach number, M, defined as follows: (2.13) Where c is the speed of sound in the Read more

Some books define the three governing equations of fluids as the Navier-Stokes equations. However, it generally defined that the Navier-Stokes equations only represent the momentum equation. We will use the “NS equation” in the rest of this book as momentum equation. Below are explanations for each of the governing equations of fluid mechanics: Mass Conservation Read more

1. Fluid Flow Parameters Pressure Pressure is defined as the force divided by the area perpendicular to the normal direction. (2.1) With F,n, and p are force vector, unit normal vector, surface area, and pressure, respectively. Figure 2.1. Normal vector of a surface By definition (in physics), this is the same as normal stress, but Read more