Developments in computational methods for high-lift aerodynamics

1988 ◽  
Vol 92 (917) ◽  
pp. 265-288 ◽  
Author(s):  
D. A. King ◽  
B. R. Williams
Keyword(s):  
Separated Flow ◽  
Direct Methods ◽  
Viscous Flows ◽  
Inviscid Flow ◽  
Contributory Factor ◽  
High Lift ◽  
First Order ◽  
Boundary Layer Equations ◽  
Attached Flow ◽  
The Uk

SummaryViscous/inviscid interaction techniques for calculating the flow about multiple-element aerofoils have been under development in the UK for the last decade producing such programs as MAVIS and HILDA. These methods give reasonable predictions of the lift for viscous attached flow, but fail to give an estimate of the maximum lift and the associated flow separations on the aerofoils. The methods also fail to give adequate predictions of the drag for both attached and separated flow. The disappointing performance of the methods in predicting maximum lift stems primarily from the use of direct methods to solve the first order boundary-layer equations, whilst the poor drag predictions arise from inadequate methods for predicting the development of the flow over the flap. The assumption of incompressible flow could also be a contributory factor in both cases. Methods of overcoming the first restriction are described by using a more appropriate coupling between the inviscid and viscous flows which properly assigns the correct role to each partner in the coupling: this approach is illustrated by ‘semi-inverse’ and ‘quasi-simultaneous’ couplings of a finite-element method for the compressible inviscid flow with an integral method for the boundary layers and wakes. Some methods for calculating the compressible flow about multiple-element aerofoils are also reviewed. However these improvements do not give an adequate estimate of the drag so possible improvements to the calculation of the flow over the flap are discussed.

Sparse identification of nonlinear unsteady aerodynamics of the oscillating airfoil

2020 ◽  
pp. 095441002095987
Author(s):  
Chong Sun ◽  
Tian Tian ◽  
Xiaocheng Zhu ◽  
Zhaohui Du
Keyword(s):  
Flow Model ◽  
Dynamic Change ◽  
Unsteady Aerodynamics ◽  
Separated Flow ◽  
General System ◽  
Training Data ◽  
Loop Control ◽  
First Order ◽  
Attached Flow ◽  
Unsteady Lift

Reduced-order models are widely used in aerospace engineering. A model for unsteady aerodynamics is desirable for designing the blades of wind turbines. Recently, sparse identification of nonlinear dynamics with control was introduced to identify the parameters of an input-output dynamical system. In this paper, two models for attached flows and one for separated flows are identified through this technique. For the unsteady lift of the attached flow, Model I is a linear model that presents the dynamic change of an unsteady lift to a static lift. Model II was built based on Model I in order to obtain a more general system with closed-loop control. It has a first-order inert element that delays the overall input of the static lift. The Model II results replicate the training data very well and give an accurate prediction of other oscillating cases with different oscillation amplitudes, reduced frequency or mean angle of attack. For the unsteady lift of the separated flow, Model III is identified as a nonlinear model, which also has a first-order inert element. This model captures the nonlinear aerodynamics of the separated flow and replicates the training cases well. In addition, the prediction of Model III has good agreement with the numerical results.

scholarly journals Numerical analysis of high-lift configurations with oscillating flaps

2021 ◽  
Author(s):  
Johannes Ruhland ◽  
Christian Breitsamter
Keyword(s):  
Reynolds Number ◽  
Flow Separation ◽  
Separated Flow ◽  
Navier Stokes ◽  
Rotational Axis ◽  
High Lift ◽  
Hinge Point ◽  
Reduced Frequency ◽  
Flap Deflection ◽  
The Impact

AbstractThis study presents two-dimensional aerodynamic investigations of various high-lift configuration settings concerning the deflection angles of droop nose, spoiler and flap in the context of enhancing the high-lift performance by dynamic flap movement. The investigations highlight the impact of a periodically oscillating trailing edge flap on lift, drag and flow separation of the high-lift configuration by numerical simulations. The computations are conducted with regard to the variation of the parameters reduced frequency and the position of the rotational axis. The numerical flow simulations are conducted on a block-structured grid using Reynolds Averaged Navier Stokes simulations employing the shear stress transport $$k-\omega $$ k - ω turbulence model. The feature Dynamic Mesh Motion implements the motion of the oscillating flap. Regarding low-speed wind tunnel testing for a Reynolds number of $$0.5 \times 10^{6}$$ 0.5 × 10 6 the flap movement around a dropped hinge point, which is located outside the flap, offers benefits with regard to additional lift and delayed flow separation at the flap compared to a flap movement around a hinge point, which is located at 15 % of the flap chord length. Flow separation can be suppressed beyond the maximum static flap deflection angle. By means of an oscillating flap around the dropped hinge point, it is possible to reattach a separated flow at the flap and to keep it attached further on. For a Reynolds number of $$20 \times 10^6$$ 20 × 10 6 , reflecting full scale flight conditions, additional lift is generated for both rotational axis positions.

Loading Distribution Effects on Separated Flow Transition of Ultra-High-Lift Turbine Blades

2014 ◽  
Vol 30 (3) ◽  
pp. 845-856 ◽  
Author(s):  
F. Satta ◽  
D. Simoni ◽  
M. Ubaldi ◽  
P. Zunino ◽  
F. Bertini
Keyword(s):  
Turbine Blades ◽  
Separated Flow ◽  
Flow Transition ◽  
High Lift

Redesign of High-Lift LP-Turbine Airfoils for Low Speed Testing

2010 ◽  
Author(s):  
Michele Marconcini ◽  
Filippo Rubechini ◽  
Roberto Pacciani ◽  
Andrea Arnone ◽  
Francesco Bertini
Keyword(s):  
Separated Flow ◽  
Low Pressure ◽  
High Lift ◽  
Low Speed ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Flow Configurations ◽  
Artificial Neural Network Ann ◽  
Lp Turbine ◽  
Turbine Airfoils

Low pressure turbine airfoils of the present generation usually operate at subsonic conditions, with exit Mach numbers of about 0.6. To reduce the costs of experimental programs it can be convenient to carry out measurements in low speed tunnels in order to determine the cascades performance. Generally speaking, low speed tests are usually carried out on airfoils with modified shape, in order to compensate for the effects of compressibility. A scaling procedure for high-lift, low pressure turbine airfoils to be studied in low speed conditions is presented and discussed. The proposed procedure is based on the matching of a prescribed blade load distribution between the low speed airfoil and the actual one. Such a requirement is fulfilled via an Artificial Neural Network (ANN) methodology and a detailed parameterization of the airfoil. A RANS solver is used to guide the redesign process. The comparison between high and low speed profiles is carried out, over a wide range of Reynolds numbers, by using a novel three-equation, transition-sensitive, turbulence model. Such a model is based on the coupling of an additional transport equation for the so-called laminar kinetic energy (LKE) with the Wilcox k–ω model and it has proven to be effective for transitional, separated-flow configurations of high-lift cascade flows.

Compressible Boundary Layer-Inviscid Flow Interactions in Entrance Region of Internal Flows

1967 ◽  
Vol 89 (4) ◽  
pp. 281-288 ◽  
Author(s):  
V. D. Blankenship ◽  
P. M. Chung
Keyword(s):  
Boundary Layer ◽  
Shock Tube ◽  
Inviscid Flow ◽  
Perturbation Parameter ◽  
Entrance Region ◽  
Compressible Boundary Layer ◽  
Internal Flows ◽  
Flow Equations ◽  
Boundary Layer Equations ◽  
Interaction Problem

The coupling between the inviscid flow and the compressible boundary layer in the developing entrance region for internal flows is analyzed by solving the particular inviscid flow-boundary layer interaction problem. The interaction problem is solved by postulating certain series forms of solutions for the inviscid region and the boundary layer. The boundary-layer equations and inviscid-flow equations are perturbed to third order and each generated equation is solved numerically. In order to preserve the universality of each of the perturbed boundary-layer equations, the perturbation parameter is described by an integral equation which is also solved in series form. The final results describing the interaction problem are then constructed for any given conditions by forming the three series to a consistent order of magnitude. This technique of coordinate perturbation is generalized to show how it may be applied to the entrance regions of pipe flows, including mass injection or suction, and also to the laminar boundary layers in shock tube flows. It demonstrates analytically the manner in which the boundary layer and inviscid flow interact and create a streamwise pressure gradient. In particular, the interaction problem which occurs in shock tube flows is solved in detail by the use of this generalized method, as an example.

A Viscous-Inviscid Interaction Procedure—Part 1: Method for Computing Two-Dimensional Incompressible Separated Channel Flows

1986 ◽  
Vol 108 (1) ◽  
pp. 64-70 ◽  
Author(s):  
O. K. Kwon ◽  
R. H. Pletcher
Keyword(s):  
Experimental Data ◽  
Finite Difference ◽  
Turbulent Flows ◽  
Inviscid Flow ◽  
Companion Paper ◽  
Separated Flows ◽  
Two Dimensional ◽  
Boundary Layer Equations ◽  
Interaction Scheme ◽  
Laminar And Turbulent Flows

A viscous-inviscid interaction scheme has been developed for computing steady incompressible laminar and turbulent flows in two-dimensional duct expansions. The viscous flow solutions are obtained by solving the boundary-layer equations inversely in a coupled manner by a finite-difference scheme; the inviscid flow is computed by numerically solving the Laplace equation for streamfunction using an ADI finite-difference procedure. The viscous and inviscid solutions are matched iteratively along displacement surfaces. Details of the procedure are presented in the present paper (Part 1), along with example applications to separated flows. The results compare favorably with experimental data. Applications to turbulent flows over a rearward-facing step are described in a companion paper (Part 2).

An Investigation of Flow Fields Over Multi-Element Aerofoils

2001 ◽  
Vol 124 (1) ◽  
pp. 154-165 ◽  
Author(s):  
S. R. Maddah ◽  
H. H. Bruun
Keyword(s):  
Flow Field ◽  
Computational Study ◽  
Separated Flow ◽  
Mean Flow ◽  
Model Configuration ◽  
Attached Flow ◽  
The Mean ◽  
Flap Deflection ◽  
Comparative Results ◽  
Lift And Drag

This paper presents results obtained from a combined experimental and computational study of the flow field over a multi-element aerofoil with and without an advanced slat. Detailed measurements of the mean flow and turbulent quantities over a multi-element aerofoil model in a wind tunnel have been carried out using stationary and flying hot-wire (FHW) probes. The model configuration which spans the test section 600mm×600mm, is made of three parts: 1) an advanced (heel-less) slat, 2) a NACA 4412 main aerofoil and 3) a NACA 4415 flap. The chord lengths of the elements were 38, 250 and 83 mm, respectively. The results were obtained at a chord Reynolds number of 3×105 and a free Mach number of less than 0.1. The variations in the flow field are explained with reference to three distinct flow field regimes: attached flow, intermittent separated flow, and separated flow. Initial comparative results are presented for the single main aerofoil and the main aerofoil with a nondeflected flap at angles of attacks of 5, 10, and 15 deg. This is followed by the results for the three-element aerofoil with emphasis on the slat performance at angles of attack α=10, 15, 20, and 25 deg. Results are discussed both for a nondeflected flap δf=0deg and a deflected flap δf=25deg. The measurements presented are combined with other related aerofoil measurements to explain the main interaction of the slat/main aerofoil and main aerofoil/flap both for nondeflected and deflected flap conditions. These results are linked to numerically calculated variations in lift and drag coefficients with angle of attack and flap deflection angle.

Inclusion for All or Exclusion for Everyone? UK Unemployment Policies in the Age of Austerity

2021 ◽  
pp. 133-151
Author(s):  
Alessio Bertolini
Keyword(s):  
Social Protection ◽  
Employment Protection ◽  
Contributory Factor ◽  
Social Perceptions ◽  
General Welfare ◽  
Specific Category ◽  
The Uk ◽  
Welfare Discourse ◽  
Welfare Reforms ◽  
Temporary Agency Workers

Whilst the comparative political economy literature has regarded the UK as among the least dualised countries when it comes to non-standard employment, thanks to its flexible labour market and predominantly means-tested system of social pro-tection, scholars in the precariousness literature have highlighted the increased pre-carity and insecurity of many non-standard workers, highlighting the extreme con-ditionality and punitive policies typical of the UK welfare system as an important contributory factor. This paper aims to bridge the gap between these literatures. It analyses the experience of social protection of a specific category of non-standard workers, namely temporary agency workers, in accessing both active and passive unemployment policies. It finds how welfare reforms introduced in the past two decades in association with a general welfare discourse centred on the concepts of deservingness and dependency have created important barriers in accessing un-employment protection, not just based on institutional features but also on social perceptions.

First-Order Boundary-Layer Equations

1981 ◽  
pp. 10-18
Author(s):  
Ernst Heinrich Hirschel ◽  
Wilhelm Kordulla
Keyword(s):  
Boundary Layer ◽  
First Order ◽  
Boundary Layer Equations

scholarly journals Contributory factors in surgical incidents as delineated by a confidential reporting system

2018 ◽  
Vol 100 (5) ◽  
pp. 401-405 ◽  
Author(s):  
F Mushtaq ◽  
C O’Driscoll ◽  
FCT Smith ◽  
D Wilkins ◽  
N Kapur ◽  
...  
Keyword(s):  
Adverse Events ◽  
Reporting System ◽  
Contributory Factor ◽  
Systematic Analysis ◽  
Contributory Factors ◽  
Cognitive Limitations ◽  
Surgical Errors ◽  
Policies And Procedures ◽  
The Uk ◽  
Patient Safety Incidents

Background Confidential reporting systems play a key role in capturing information about adverse surgical events. However, the value of these systems is limited if the reports that are generated are not subjected to systematic analysis. The aim of this study was to provide the first systematic analysis of data from a novel surgical confidential reporting system to delineate contributory factors in surgical incidents and document lessons that can be learned. Methods One-hundred and forty-five patient safety incidents submitted to the UK Confidential Reporting System for Surgery over a 10-year period were analysed using an adapted version of the empirically-grounded Yorkshire Contributory Factors Framework. Results The most common factors identified as contributing to reported surgical incidents were cognitive limitations (30.09%), communication failures (16.11%) and a lack of adherence to established policies and procedures (8.81%). The analysis also revealed that adverse events were only rarely related to an isolated, single factor (20.71%) – with the majority of cases involving multiple contributory factors (79.29% of all cases had more than one contributory factor). Examination of active failures – those closest in time and space to the adverse event – pointed to frequent coupling with latent, systems-related contributory factors. Conclusions Specific patterns of errors often underlie surgical adverse events and may therefore be amenable to targeted intervention, including particular forms of training. The findings in this paper confirm the view that surgical errors tend to be multi-factorial in nature, which also necessitates a multi-disciplinary and system-wide approach to bringing about improvements.

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