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Axial-Flow Gas Turbines
Published in Bijay K. Sultanian, Logan's Turbomachinery, 2019
Although current research, such as that of Nicoud et al. (1991), promises computational design of the blade profile to suit prescribed velocity distributions, blades are often laid out in the form of an airfoil along a circular arc or parabolic camber line using a chord c of from 80 to 90% of the blade length. A typical (maximum) thickness-to-chord ratio is 0.2, and this maximum thickness is located at the 40% chord position. The optimum spacing between blades at the mean diameter may be determined from the relations given by Shepherd (1956)—i.e., cs=2.5cos2α2tanα2−tanα1cosαm
Drag force and drag coefficient
Published in Mohammad H. Sadraey, Aircraft Performance, 2017
where (t/c)max is the maximum thickness-to-chord ratio of the wing, or the tail. Generally speaking, the maximum thickness-to-chord ratio for a wing is about 12%–18% and for a tail is about 9%–12%. The parameter Swet in Equation 3.13 is the wing or tail wetted area.
Transonic Flight and Aerofoils
Published in Rose G. Davies, Aerodynamics Principles for Air Transport Pilots, 2020
However, because the pressure decreases slowly over a thin wing, it will produce less lift than the aerofoil with a greater thickness to chord ratio, t/c, especially at lower air speeds. So the lift coefficient of a thin aerofoil is relatively low.
Blade thickness effect on the aerodynamic performance of an asymmetric NACA six series blade vertical axis wind turbine in low wind speed
Published in International Journal of Green Energy, 2020
Hussain Mahamed Sahed Mostafa Mazarbhuiya, Agnimitra Biswas, Kaushal Kumar Sharma
In the present study 2D unsteady RANS simulations were carried out to find out the effect of blade thickness-to-chord ratio on the aerodynamic performance of an asymmetric NACA six series blade vertical axis H-Darrieus wind turbine at different low wind speed conditions. The aerodynamic performance curves are obtained at different operating and thickness-to-chord conditions and the performance insights are corroborated with the findings from the flow physics study to come to some concrete conclusions on the effects of the thickness to chord ratio. From the study, the following conclusions can be drawn: The average moment coefficient is higher for turbine having blade t/c ratio of 0.3. The power coefficient of the turbine increases with increase in blade t/c ratio and become maximum at t/c = 0.3 at 2.4 tip speed ratio. The optimum design for efficient turbine has t/c = 0.3 which has maximum power coefficient of 0.271.The present study identifies large blade curvature to create a large diverging passage on the blade suction surface as the prominent reason for aerodynamic performance drop at a high t/c ratio, which in the present design is 0.375.If the free stream velocity is increased the maximum power coefficient is decreased for the optimal t/c = 0.3, due to large vortex shading from the suction side trailing edge of the blade.
Adaptive inner iteration processes in pressure-based method for viscous compressible flows
Published in Numerical Heat Transfer, Part B: Fundamentals, 2018
Jin-Ping Wang, Jian-Fei Zhang, Zhi-Guo Qu, Wen-Quan Tao
Three different types of flows (subsonic, transonic and supersonic flows) in a channel with a circular arc bump are computed. The test cases were used by several researchers [13–15]. The width of the channel is equal to the length of the bump, and the channel length is equal to three times of the bump length. The thickness-to-chord ratio is 10% for subsonic and transonic flows and 4% for supersonic flow. The detail parameters of boundary conditions for these flows can be checked in the reference [7].