Computational Fluid Dynamics

The journey to establishing CFD (computational fluid dynamics) began in the 1960s after establishing underlying principles of fluid dynamics and some governing equations, such as RANS, Euler, and potential flow. Its emergence between 1965 and 2005 depended on a combination of algorithms and computer power advances. It is a numerical study of steady and unsteady fluid motion. With the help of parallel supercomputers, CFD helps study how fluids behave in complex scenarios, like sound generation, turbulence, and boundary layer transition, with the use in and beyond aerospace engineering. It is applied throughout the design process of an aircraft to refine and inform both initial and advanced concepts.

Computational fluid dynamics, abbreviated as CFD, involves using computational techniques and numerical dynamics to study and analyze the behavior of gasses and liquids as they flow. It allows scientists and engineers to predict and simulate fluid flow patterns and heat transfer without conducting physical experiments (Heinz, 2023). It plays a significant role in different industries, like environmental, energy, automotive, and aerospace engineering.

In aircraft design and analysis, computational fluid dynamics helps to understand and optimize aerodynamic performance. It serves different purposes in the analysis and design of aircraft. First, CFD stimulates fluid flow over aircraft services, like fuselage, wings, and control surfaces. Analyzing the flow patterns helps aerospace engineers to understand the interaction between air and aircraft’s shape. This plays a significant role in designing more stable and efficient aircraft. Secondly, CFD reduces drag, an opposing force in an aircraft’s motion via air (Khan et al., 2019). Its simulation identifies high-drag areas and facilitates modification to the surface and shape of an aircraft, thus enhancing performance by reducing drag. Third, CFD optimizes wing design to generate appropriate lift for aircraft takeoff and flight. Aerospace engineers use it to study wing configurations, control surfaces, and attack angles, thus ensuring required lift characteristics (Khan et al., 2019). Lastly, CFD serves as a virtual wind tunnel, facilitating testing on different design variations without developing a physical prototype, saving resources and time. The following images show a virtual wind tunnel and CFD optimization of a wing design.

The CFD plays a significant role in aircraft design by offering crucial insights into the aerodynamic behavior of airplanes. Some CFD results in aircraft design are stall prediction, flow visualization, drag analysis, vortex interaction, and sensitivity analysis (Khan et al., 2019). Computational fluid dynamics helps to predict the beginning of a stall, a crucial condition whereby airflow over wings is separated, resulting in reduced lift. This calls for evaluation of design modification to prevent stalls. It visualizes airflow patterns over the surface of an aircraft, enabling engineers to identify vortices, separation regions, and other features that can adversely affect performance. Also, CFD gives results about the behavior of the boundary layer. These results are crucial as aerospace engineers use them to predict frictional effects and optimize surface treatments. Further, it is used by engineers to analyze different drag components, such as induced, pressure, and friction drag. The outcome helps to reduce drag and optimize the aircraft’s performance. Sensitivity analysis is performed using CFD to understand how design parameter changes affect an aircraft's overall performance (Khan et al., 2019). Some of these changes are engine placement, wing area, and wing sweep.

Inviscid aerodynamics represents a fluid flow that has zero or negligible viscosity. In this type of aerodynamics, engineers use CFD to analyze and simulate fluid flow without considering viscosity or viscous effects. CFD is used in different ways in inviscid aerodynamics, such as flow analysis, wing analysis, and conceptual design study (Aubin et al., 2016). Engineers use inviscid CFD to analyze the drag and lift characteristics of wings and their interaction with fluid flow, making it easier to understand aerodynamic performance. Inviscid simulations are used during the initial design phases to explore different concepts and assess their stability and efficiency. This makes it easier for engineers to come up with different design options before performing detailed viscous simulations.

Computational fluid dynamics offers different benefits across various industries and fields. First, it allows designers and engineers to virtually test designs before developing physical prototypes, reducing the need for unnecessary experiments (Rojas-Sola et al., 2016). Secondly, it helps engineers to quickly assess the effect of some changes in design on heat transfer and fluid flow, resulting in very short development cycles. Third, CFD helps to identify possible design risks by analyzing and simulating the behavior of a fluid. This results in a reduced risk of costly design errors. Lastly, it is used to study and reduce potential environmental effects, like pollutant dispersion in water bodies or the atmosphere (Rojas-Sola et al., 2016). However, CFD is limited by some factors, such as numerical errors, meshing challenges, software complexity, and lack of physical insight (Rojas-Sola et al., 2016). Its simulations comprise continuous equations or numerical methods prone to truncation errors that may result in inaccuracy. Also, generating a mesh for complicated geometries can be time-consuming and difficult. Its software packages require professionals to set up because they are sophisticated.

CFD has wide application areas beyond aerospace engineering. It is a versatile technique that can be applied to analyze and simulate fluid flow in other areas such as the automotive industry, power generation, building and construction industry, biomedical application, environmental engineering, chemical processing, and oil and gas industry. In the automotive industry, the tool is used to design and optimize automobiles, such as motorcycles, buses, trucks, and cars. It is majorly used to enhance stability, reduce drag, and optimize fuel efficiency.

References 

Aubin, N., Augier, B., Bot, P., Hauville, F., & Floch, R. (2016). Inviscid approach for upwind sails aerodynamics. How far can we go? Journal of Wind Engineering and Industrial Aerodynamics, 155, 208-215. https://doi.org/10.1016/j.jweia.2016.06.005 Heinz, S. (2023). A mathematical solution to the computational fluid dynamics (CFD) dilemma. Mathematics, 11(14), 3199. https://doi.org/10.3390/math11143199 Khan, F. N., Batul, B., & Aizaz, A. (2019). A CFD analysis of wingtip devices to improve lift and drag characteristics of aircraft wing. IOP Conference Series: Materials Science and Engineering, 642(1), 012006. https://doi.org/10.1088/1757-899x/642/1/012006 Rojas-Sola, Ignacio, J., García-Baena, Hermoso-Orzáez, & Jesús, M. (2016). A review of the computational fluid dynamics simulation software: Advantages, disadvantages and main applications. Journal of Magnetohydrodynamics and Plasma Research, 21(4), 417-424.