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- ItemModeling the compressible flow field of an impulsively started circular cylinder with refined potential flow theory(AIP Publishing, 2026-08-07) Taofiq Omoniyi Amoloye; Leke Thaddeus Oladimeji; Mahmoud A. Hayajnh; Olalekan Adebayo OlayemiUnderstanding compressible flows over bluff bodies, such as circular cylinders, is critical for applications in aerospace engineering, space exploration, and astrophysics. However, the complexity of viscous and unsteady flows, compounded by compressibility effects, remains a challenge for experimental and computational methods. This study explores the compressible flow field of an impulsively started circular cylinder using Refined Potential Flow Theory (RPT), an analytical model that extends classical potential flow theory to include compressibility effects. The governing equations, boundary conditions, and refined stream function are developed to capture the density, velocity, and pressure fields in subsonic and transonic regimes. The results demonstrate that compressibility marginally increases vortex enstrophy at low Reynolds numbers, while its influence on wake flow stability diminishes at higher values. The study reveals that compressibility suppresses shear layer instability, reduces wake velocity deficits, and introduces smaller-scale structures that disrupt the inertial range of turbulence in the low subsonic regime. At higher Mach numbers (M∞≥0.6), local supersonic pockets and shock waves emerge, forming complex λ-shock systems and bow shocks. The predictions of the Strouhal number from RPT show marginal changes for 0.2≤M∞≤0.5, consistent with experimental and computational trends. Although RPT aligns with existing methods to capture key flow features, discrepancies in wake stability and recirculation zone dimensions highlight areas for further refinement. This research underscores the potential of RPT in developing optimization tools that complement experimental and numerical studies, offering valuable insights into compressible flow physics for engineering applications in high-altitude flight and space exploration.
- ItemModeling the unsteady wake of an impulsively started circular cylinder using refined potential flow theory(IOP Publishing Ltd, 2024-07-08) Taofiq O AmoloyeCylindrical structures find usage in many engineering applications including tethered oil drums and engine canisters slung beneath helicopters in flight. The motion of air around such circular cylindrical structures and the helicopter presents interesting phenomena including flow separation, wakes and turbulence. The physics of these are enshrined in the continuity equation and the Navier–Stokes equations. Therefore, their studies are not only important in mathematics and physics, but they are also required for efficient helicopter operations. In practice, reduced-order models of these operations that take in aerodynamics models of the tethered loads are utilized for stability analysis, flight certification and pilot training because of the prohibitive cost of experimentation and computational analyses of these configurations. However, there is a dearth of realistic analytical models of finite cylinder flows because of the Navier–Stokes problem. Classical potential flow theory provides an avenue to develop such models, but the extant gaps in its predictions significantly preclude its usage for engineering applications. Attempting to bridge these gaps, this article introduces refined potential flow theory in which the governing equations and boundary conditions are satisfied. Viscous effects, fluctuations of the mean flow and three-dimensional effects are also incorporated. For characterization, refined potential flow theory is employed on an incompressible flow over an impulsively started circular cylinder for Reynolds numbers and non-dimensional times in the range 30 < Re < 10^4 and 0.2 ≤ T ≤ 77, 047 respectively. There is an excellent prediction of 0.209 for the Strouhal number at Re = 3, 900. At this transitional Reynolds number, the harmonics of the Strouhal frequency are also captured, and the characteristic irregular fluctuations at sub-Strouhal frequencies are discernible in the velocity spectra. As the flow becomes more turbulent, these become more pronounced at Re = 9, 500 when the predicted Strouhal number is within 10% of experimental result. In the fully developed stage, spectra analyses of the wake velocity components at some downstream locations also display Kolmogorov's Five-Thirds law of homogeneous isotropic turbulence. The present model can thus aid the development of reduced-order models of helicopter operations that feature tethered cylindrical loads.
- ItemComputational Development and Aerodynamic Analysis of a Single-Stage Launch Vehicle to Subdue Post-Launch Risk(FETiCON, 2023-06-05) Jinadu Abdulbaqi; Koloskov V.; Dmytro T.; Oluwatofunmi A. M; Olayemi A. OlalekanThe aerospace industry has prioritized reducing fatalities and failure rates after the launch of a vehicle resulting from system or engine failure. Rocketry has been difficult over the years, and international players in the industry are constantly attempting to learn from any failures. This paper aims to decrease material, resource, and payload waste while ensuring crew safety by focusing on the computational modelling and aerodynamic analysis of a single-stage launch vehicle. CATIA V5 was utilized to create the computational model of a triggered nose cone rocket booster while ANSYS was used to analyse the trigger nose cone at different angles of attack and determine how the trigger nose cone will behave in case of emergencies such as system or engine failure, which could lead to the complete explosion of the launch vehicle. Based on the current findings, the trigger nose cone is not in the safe zone when ejected at an angle of attack greater than 20° due to the shockwave's effect on its surface when ejected from the main body of the launch vehicle.
- ItemCFD Analysis of A 3-Bladed NACA 0018 Vertical Axis Wind Turbine for Deployment in Ilorin, Kwara State, Nigeria(FETiCON, 2023-06-05) Olayemi Adebayo Olalekan; Ajide Favour Tomisin; Ibitoye Emmanuel Segun; Obalalu Martins Adebowale; Jinadu Abdulbaqi; Anyaegbuna Elochukwu BenjaminDuring the last few years, vertical axis wind tubines have evolved as a suitable supplement to energy production worldwide. There has been a lot of interest in vertical axis wind turbines as a small-scale renewable power converter because they can be used in places where the wind speeds are turbulent or unsteady. When investigating the aerodynamic characteristics of vertical axis wind turbines, computational fluid dynamics has been shown to be one of the most effective methods. There is a need for better knowledge of the factors that influence the accuracy of computational fluid dynamics. The aim of this paper is to demonstrate the influence of these factors on the simulation of a low-speed turbine to guide the execution of accurate computational fluid dynamics simulations of vertical axis wind turbines at varying tip speed ratios and solidities. To simulate the turbulent, unstable fluid flow around the turbine, we used a 2D SIMPLE approach with the help of ANSYS FLUENT. In the study, it was found that when the tip speed ratio is low, the result is largely dependent on the azimuthal increment, and a fine azimuthal increment of 0.1 is usually better for low tip speed ratios
- ItemCFD Analysis of a 3-bladed NACA 0018 Vertical Axis Wind Turbine for Deployment in Ilorin, Kwara State, Nigeria.(FETiCON, 2023-06-05) Olayemi O. A.; Ajide T. F.; Obalalu A. M.; Ibitoye S. E.; Jinadu Abdulbaqi; Anyaegbun B. E.The aerospace industry has prioritized reducing fatalities and failure rates after the launch of a vehicle resulting from system or engine failure. Rocketry has been difficult over the years, and international players in the industry are constantly attempting to learn from any failures. This paper aims to decrease material, resource, and payload waste while ensuring crew safety by focusing on the computational modelling and aerodynamic analysis of a single-stage launch vehicle. CATIA V5 was utilized to create the computational model of a triggered nose cone rocket booster while ANSYS was used to analyse the trigger nose cone at different angles of attack and determine how the trigger nose cone will behave in case of emergencies such as system or engine failure, which could lead to the complete explosion of the launch vehicle. Based on the current findings, the trigger nose cone is not in the safe zone when ejected at an angle of attack greater than 20° due to the shockwave's effect on its surface when ejected from the main body of the launch vehicle.