Did not invent CFD but created the practice of CFD – its application to problems of interest to engineers.
Author: Dr. Sandeep Mouvanal
Professor Brain Spalding was a distinguished academic and mechanical engineer from Britain, who was renowned for his significant contributions to computational fluid dynamics (CFD) and heat transfer. Born in 1923, he received his education from the Imperial College of London and later served as a professor and Head of the Thermodynamics Division there. B. Spalding is well-known for his pioneering work in developing numerical methods for solving complex fluid dynamics problems, which have had a profound impact on engineering design and analysis, leading to the widespread use of CFD in diverse applications. He received several accolades and honors, including the ASME Heat Transfer Memorial Award, the Medal of the Japan Society of Mechanical Engineers, and the Rumford Medal of the Royal Society, for his outstanding research contributions. 
The work of Professor Brian Spalding, in collaboration with his students and colleagues, played a transformative role in the field of computational fluid dynamics (CFD). While he was not the inventor of CFD or even the originator of the term, Professor Spalding was instrumental in developing CFD into a practical tool for practicing engineers. Under his leadership, the Imperial College group made significant contributions to the development of numerical methods for solving complex fluid dynamics problems, which led to the creation of several commercially available CFD software tools that engineers still use today. Professor Spalding’s pioneering work helped to bring CFD out of the realm of esoteric and mathematical science and into the mainstream as a fully developed tool for solving practical engineering problems. 
Portrait of Brian Spalding, watercolor on paper (15 x 11″, Artist: Dr.Sandeep Mouvanal)
Some Important Contributions:
- Pioneering work in computational fluid dynamics (CFD): Professor Spalding’s early work in the 1960s laid the foundation for modern CFD. He developed numerical methods for solving complex fluid dynamics problems, including the SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) algorithm, which has since become a widely-used method in CFD.
- Development of commercial CFD software: Professor Spalding co-founded the company CHAM (Concentration, Heat, And Momentum Limited ), which developed commercial CFD software packages, including PHOENICS (Parabolic, Hyperbolic Or Elliptic Numerical Integration Code Series), used in various industries.
- Contributions to turbulent flow research: Professor Spalding developed methods for simulating and analyzing turbulent flows, including the k-epsilon model, which is a widely-used turbulence model in CFD
- Application of CFD to industrial problems: Professor Spalding’s work in developing CFD and heat transfer analysis methods has led to their widespread use in various industries, such as aerospace, automotive, and chemical engineering. His contributions have enabled engineers to improve the design of complex systems, reduce costs, and improve safety.
- Heat transfer research: Professor Spalding made significant contributions to the field of heat transfer, particularly in the development of numerical methods for analyzing heat transfer in complex systems, such as boilers and heat exchangers.
- Combustion research: Professor Brian Spalding made significant contributions to combustion research, including the development of numerical methods and combustion models, the study of flame dynamics, and the application of CFD to combustion systems. He studied the dynamics of flames, particularly in relation to the effects of turbulence. His work helped to improve our understanding of how turbulence affects flame propagation and stability. He developed several combustion models, including the eddy break-up model and the laminar flamelet model. These models have been widely used in CFD simulations of combustion systems.
The Unified Theory
In his book “Convective Mass Transfer” , Professor Brian Spalding aimed to integrate the fields of heat transfer and mass transfer by considering simultaneous heat and mass transfer, including phenomena such as evaporation, ablation, and combustion, within a single framework. Professor Brian Spalding’s research theme throughout his professional career was the unification of flow, heat, and mass transport. He faced the challenge of creating a single calculation method for turbulent shear layers, which included boundary layers, jets, wakes, wall jets, and duct flows in the presence of pressure gradient and mass transfer. This effort resulted in the development of the Unified Theory, which has had a significant impact on the CFD community.
The SIMPLE algorithm
The paper by Patankar and Spalding  described the Semi-Implicit Method for Pressure-Linked Equations (SIMPLE), which has become a widely used numerical method for solving fluid flow problems. The method involves calculating the streamwise velocity component by solving the streamwise momentum equation with a constant value of dp/dx across the cross-stream plane. The cross-stream velocity components and cross-stream pressure variation are then calculated by solving the cross-stream momentum equations and continuity equation. This method has been shown to be effective in solving a range of flow problems and has been implemented in various commercial CFD software packages. The method quickly gained popularity and became widely used worldwide. Researchers subsequently developed improved variants of the method, including SIMPLEC, SIMPLER, and SIMPLEST, which strengthened the coupling between velocity and pressure and provided more robust algorithms with faster convergence. These advancements have made the method even more widely used and effective in solving complex fluid flow problems.
The PHOENICS code
The development of the Parabolic, Hyperbolic Or Elliptic Numerical Integration Code Series, PHOENICS , resulted in a practical piece of CFD software that helped create a whole industry and generated jobs and wealth where none existed before. As a subset of computer-aided engineering, CFD owes its growth to the advancements made by PHOENICS. The software made complex fluid flow problems more accessible and enabled engineers to simulate and analyze fluid flow, heat transfer, and other phenomena. The impact of PHOENICS on the CFD industry cannot be overstated.
 “Brian Spalding” Wikipedia, Wikimedia Foundation, 13 Dec 2022, https://en.wikipedia.org/wiki/Brian_Spalding
 Runchal, Akshai K. “Brian Spalding: CFD and reality–A personal recollection.” International Journal of Heat and Mass Transfer 52.17-18 (2009): 4063-4073.
 Artemov, V., et al. “A tribute to DB Spalding and his contributions in science and engineering.” International Journal of Heat and Mass Transfer 52.17-18 (2009): 3884-3905.
 D.B. Spalding, Convective Mass Transfer; an Introduction, Edward, Arnold, London, 1963.
 S.V. Patankar, D.B. Spalding, A calculation procedure for heat, mass and momentum transfer in three-dimensional parabolic flows, Int. J. Heat Mass Transfer 15 (10) (1972) 1787–1806.
 D.B. Spalding, PHOENICS a general-purpose computer program for multidimensional one- and two-phase flow, Math. Comput. Simul. XXIII (1981) 267–276.
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