The Experts below are selected from a list of 882 Experts worldwide ranked by ideXlab platform

Thomas Robin Barrett - One of the best experts on this subject based on the ideXlab platform.

  • Aerodynamic design optimization using flow feature parameterization
    Analysis, 2007
    Co-Authors: Thomas Robin Barrett
    Abstract:

    Design optimization methods using high-fidelity computational fluid dynamics simulations are becoming increasingly popular in the area of aerodynamic design, sustaining the desire to make these methods more computationally efficient. Such design strategies typically define the aerodynamic product using a parametric model of the geometry, but this can often require a large number of design variables, increasing the computational cost. This thesis proposes that a parametric model of aerodynamic flow features, rather than geometry, can be a parsimonious method of representing designs, giving a reduction in the number of design parameters required for optimization. The parameterization of flow features is coupled with inverse design, in order to recover the corresponding geometry. While an expensive analysis code is used in evaluating design performance, computational cost is reduced by using a low-fidelity code in the inverse design process. This newly presented method is demonstrated using four case studies in 2-D airfoil design, in which the parameterized flow feature is the surface pressure distribution, and two case studies for 3-D wing design, in which the Spanwise Loading distribution is parameterized. These strategies are consistently compared against a benchmark design search method which uses a conventional parameterization of the geometry. The two methods are described in detail, and their relative performance is analysed and discussed. The newly presented method is found to converge towards the optimum design significantly more quickly than the benchmark method, providing designs with greater performance for a given computational expense. A parameterization of flow features can generate designs with higher quality and detail than a geometry-based method of the same dimensionality.

Gunn E - One of the best experts on this subject based on the ideXlab platform.

  • Stall Inception in Low-Pressure Ratio Fans
    'Organisation for Economic Co-Operation and Development (OECD)', 2019
    Co-Authors: Kim S, Pullan Graham, Hall Cesare, Rp Grewe, Mj Wilson, Gunn E
    Abstract:

    A combined experimental and computational test programme, with two low pressure ratio aero-engine fans, has been used to identify the flow mechanisms at stall inception and the subsequent stall cell growth. The two fans have the same rotor tip clearance, annulus design and downstream stators, but different levels of tip Loading. The measurement data show that both fans stall via spike-type inception, but that the growth of the stall cell, and the final cell size, is different in each fan. The computations, reproducing both the qualitative and quantitative behaviour of the steady-state and transient measurements, are used to identify the flow mechanisms at the origin of stall inception. In one fan, spillage of tip leakage flow upstream of the leading edge plane is responsible. In the other, sudden growth of casing corner separation blockage leads to stall. These two mechanisms are in accord with the findings from core compressors. However, the transonic aerodynamics and low hub-to-tip radius ratio of the fans leads to the following two findings: first, the casing corner separation is driven by shock-boundary layer interaction; second, the Spanwise Loading distribution of the fan determines whether the spike develops into full-span or part-span stall and both types of behaviour are represented in the present work. Finally, the axial momentum flux of the tip clearance flow is shown to be a useful indicator of the leakage jet spillage mechanism. A simple model is provided that links the tip Loading, stagger and solidity with the tip clearance axial momentum flux, thereby allowing the aerodynamicist to connect, qualitatively, design parameters with the stall behaviour of the fan

  • Stall Inception in Low-Pressure Ratio Fans
    American Society of Mechanical Engineers, 2019
    Co-Authors: Kim S, Rp Grewe, Mj Wilson, Pullan G, Ca Hall, Gunn E
    Abstract:

    © 2019 by ASME. A combined experimental and computational test program, with two low-pressure ratio aero-engine fans, has been used to identify the flow mechanisms at stall inception and the subsequent stall cell growth. The two fans have the same rotor tip clearance, annulus design, and downstream stators, but different levels of tip Loading. The measurement data show that both the fans stall via spike-type inception, but that the growth of the stall cell and the final cell size is different in each fan. The computations, reproducing both the qualitative and quantitative behavior of the steady-state and transient measurements, are used to identify the flow mechanisms at the origin of stall inception. In one fan, spillage of tip leakage flow upstream of the leading edge plane is responsible. In the other, sudden growth of casing corner separation blockage leads to stall. These two mechanisms are in accord with the findings from core compressors. However, the transonic aerodynamics and the low hub-to-tip radius ratio of the fans lead to the following two findings: first, the casing corner separation is driven by shock-boundary layer interaction and second, the Spanwise Loading distribution of the fan determines whether the spike develops into full-span or part-span stall and both types of behavior are represented in the present work. Finally, the axial momentum flux of the tip clearance flow is shown to be a useful indicator of the leakage jet spillage mechanism. A simple model is provided that links the tip Loading, stagger, and solidity with the tip clearance axial momentum flux, thereby allowing the aerodynamicist to connect, qualitatively, design parameters with the stall behavior of the fan

  • Stall inception in low pressure ratio fans
    2018
    Co-Authors: Kim S, Rp Grewe, Mj Wilson, Pullan G, Ca Hall, Gunn E
    Abstract:

    Copyright © 2018 ASME. A combined experimental and computational test programme, with two low pressure ratio aero-engine fans, has been used to identify the flow mechanisms at stall inception and the subsequent stall cell growth. The two fans have the same rotor tip clearance, annulus design and downstream stators, but different levels of tip Loading. The measurement data show that both fans stall via spike-type inception, but that the growth of the stall cell, and the final cell size, is different in each fan. The computations, reproducing both the qualitative and quantitative behaviour of the steady-state and transient measurements, are used to identify the flow mechanisms at the origin of stall inception. In one fan, spillage of tip leakage flow upstream of the leading edge plane is responsible. In the other, sudden growth of casing corner separation blockage leads to stall. These two mechanisms are in accord with the findings from core compressors. However, the transonic aerodynamics and low hub-to-tip radius ratio of the fans leads to the following two findings: First, the casing corner separation is driven by shock-boundary layer interaction; second, the Spanwise Loading distribution of the fan determines whether the spike develops into full-span or part-span stall and both types of behaviour are represented in the present work. Finally, the axial momentum flux of the tip clearance flow is shown to be a useful indicator of the leakage jet spillage mechanism. A simple model is provided that links the tip Loading, stagger and solidity with the tip clearance axial momentum flux, thereby allowing the aerodynamicist to connect, qualitatively, design parameters with the stall behaviour of the fan

Kamran Mohseni - One of the best experts on this subject based on the ideXlab platform.

  • a vortex model for forces and moments on low aspect ratio wings in side slip with experimental validation
    Proceedings of The Royal Society A: Mathematical Physical and Engineering Sciences, 2017
    Co-Authors: Adam Devoria, Kamran Mohseni
    Abstract:

    This paper studies low-aspect-ratio ([Formula: see text]) rectangular wings at high incidence and in side-slip. The main objective is to incorporate the effects of high angle of attack and side-slip into a simplified vortex model for the forces and moments. Experiments are also performed and are used to validate assumptions made in the model. The model asymptotes to the potential flow result of classical aerodynamics for an infinite aspect ratio. The [Formula: see text] → 0 limit of a rectangular wing is considered with slender body theory, where the side-edge vortices merge into a vortex doublet. Hence, the velocity fields transition from being dominated by a Spanwise vorticity monopole ([Formula: see text] ≫ 1) to a streamwise vorticity dipole ([Formula: see text] ∼ 1). We theoretically derive a Spanwise Loading distribution that is parabolic instead of elliptic, and this physically represents the additional circulation around the wing that is associated with reattached flow. This is a fundamental feature of wings with a broad-facing leading edge. The experimental measurements of the Spanwise circulation closely approximate a parabolic distribution. The vortex model yields very agreeable comparison with direct measurement of the lift and drag, and the roll moment prediction is acceptable for [Formula: see text] ≤ 1 prior to the roll stall angle and up to side-slip angles of 20°.

Kim S - One of the best experts on this subject based on the ideXlab platform.

  • Stall Inception in Low-Pressure Ratio Fans
    'Organisation for Economic Co-Operation and Development (OECD)', 2019
    Co-Authors: Kim S, Pullan Graham, Hall Cesare, Rp Grewe, Mj Wilson, Gunn E
    Abstract:

    A combined experimental and computational test programme, with two low pressure ratio aero-engine fans, has been used to identify the flow mechanisms at stall inception and the subsequent stall cell growth. The two fans have the same rotor tip clearance, annulus design and downstream stators, but different levels of tip Loading. The measurement data show that both fans stall via spike-type inception, but that the growth of the stall cell, and the final cell size, is different in each fan. The computations, reproducing both the qualitative and quantitative behaviour of the steady-state and transient measurements, are used to identify the flow mechanisms at the origin of stall inception. In one fan, spillage of tip leakage flow upstream of the leading edge plane is responsible. In the other, sudden growth of casing corner separation blockage leads to stall. These two mechanisms are in accord with the findings from core compressors. However, the transonic aerodynamics and low hub-to-tip radius ratio of the fans leads to the following two findings: first, the casing corner separation is driven by shock-boundary layer interaction; second, the Spanwise Loading distribution of the fan determines whether the spike develops into full-span or part-span stall and both types of behaviour are represented in the present work. Finally, the axial momentum flux of the tip clearance flow is shown to be a useful indicator of the leakage jet spillage mechanism. A simple model is provided that links the tip Loading, stagger and solidity with the tip clearance axial momentum flux, thereby allowing the aerodynamicist to connect, qualitatively, design parameters with the stall behaviour of the fan

  • Stall Inception in Low-Pressure Ratio Fans
    American Society of Mechanical Engineers, 2019
    Co-Authors: Kim S, Rp Grewe, Mj Wilson, Pullan G, Ca Hall, Gunn E
    Abstract:

    © 2019 by ASME. A combined experimental and computational test program, with two low-pressure ratio aero-engine fans, has been used to identify the flow mechanisms at stall inception and the subsequent stall cell growth. The two fans have the same rotor tip clearance, annulus design, and downstream stators, but different levels of tip Loading. The measurement data show that both the fans stall via spike-type inception, but that the growth of the stall cell and the final cell size is different in each fan. The computations, reproducing both the qualitative and quantitative behavior of the steady-state and transient measurements, are used to identify the flow mechanisms at the origin of stall inception. In one fan, spillage of tip leakage flow upstream of the leading edge plane is responsible. In the other, sudden growth of casing corner separation blockage leads to stall. These two mechanisms are in accord with the findings from core compressors. However, the transonic aerodynamics and the low hub-to-tip radius ratio of the fans lead to the following two findings: first, the casing corner separation is driven by shock-boundary layer interaction and second, the Spanwise Loading distribution of the fan determines whether the spike develops into full-span or part-span stall and both types of behavior are represented in the present work. Finally, the axial momentum flux of the tip clearance flow is shown to be a useful indicator of the leakage jet spillage mechanism. A simple model is provided that links the tip Loading, stagger, and solidity with the tip clearance axial momentum flux, thereby allowing the aerodynamicist to connect, qualitatively, design parameters with the stall behavior of the fan

  • Stall inception in low pressure ratio fans
    2018
    Co-Authors: Kim S, Rp Grewe, Mj Wilson, Pullan G, Ca Hall, Gunn E
    Abstract:

    Copyright © 2018 ASME. A combined experimental and computational test programme, with two low pressure ratio aero-engine fans, has been used to identify the flow mechanisms at stall inception and the subsequent stall cell growth. The two fans have the same rotor tip clearance, annulus design and downstream stators, but different levels of tip Loading. The measurement data show that both fans stall via spike-type inception, but that the growth of the stall cell, and the final cell size, is different in each fan. The computations, reproducing both the qualitative and quantitative behaviour of the steady-state and transient measurements, are used to identify the flow mechanisms at the origin of stall inception. In one fan, spillage of tip leakage flow upstream of the leading edge plane is responsible. In the other, sudden growth of casing corner separation blockage leads to stall. These two mechanisms are in accord with the findings from core compressors. However, the transonic aerodynamics and low hub-to-tip radius ratio of the fans leads to the following two findings: First, the casing corner separation is driven by shock-boundary layer interaction; second, the Spanwise Loading distribution of the fan determines whether the spike develops into full-span or part-span stall and both types of behaviour are represented in the present work. Finally, the axial momentum flux of the tip clearance flow is shown to be a useful indicator of the leakage jet spillage mechanism. A simple model is provided that links the tip Loading, stagger and solidity with the tip clearance axial momentum flux, thereby allowing the aerodynamicist to connect, qualitatively, design parameters with the stall behaviour of the fan

Adam Devoria - One of the best experts on this subject based on the ideXlab platform.

  • a vortex model for forces and moments on low aspect ratio wings in side slip with experimental validation
    Proceedings of The Royal Society A: Mathematical Physical and Engineering Sciences, 2017
    Co-Authors: Adam Devoria, Kamran Mohseni
    Abstract:

    This paper studies low-aspect-ratio ([Formula: see text]) rectangular wings at high incidence and in side-slip. The main objective is to incorporate the effects of high angle of attack and side-slip into a simplified vortex model for the forces and moments. Experiments are also performed and are used to validate assumptions made in the model. The model asymptotes to the potential flow result of classical aerodynamics for an infinite aspect ratio. The [Formula: see text] → 0 limit of a rectangular wing is considered with slender body theory, where the side-edge vortices merge into a vortex doublet. Hence, the velocity fields transition from being dominated by a Spanwise vorticity monopole ([Formula: see text] ≫ 1) to a streamwise vorticity dipole ([Formula: see text] ∼ 1). We theoretically derive a Spanwise Loading distribution that is parabolic instead of elliptic, and this physically represents the additional circulation around the wing that is associated with reattached flow. This is a fundamental feature of wings with a broad-facing leading edge. The experimental measurements of the Spanwise circulation closely approximate a parabolic distribution. The vortex model yields very agreeable comparison with direct measurement of the lift and drag, and the roll moment prediction is acceptable for [Formula: see text] ≤ 1 prior to the roll stall angle and up to side-slip angles of 20°.