Unsteady Hydrofoils: Theoretical and Computational Analysis

2013 ◽  
Author(s):  
Daniel T. Valentine
Keyword(s):  
Flat Plate ◽  
Computational Analysis ◽  
Vortex Sheet ◽  
Vortex Wake ◽  
Two Dimensional ◽  
Fixed Angle ◽  
Induced Drag ◽  
Wake Model ◽  
Theoretical Results ◽  
Computational Predictions

In this paper the computational problem examined is the impulsive start of a two-dimensional flat-plate hydrofoil at a fixed angle of attack. The method applied is an equally-spaced lumped-vortex panel method. The results from a lumped-vortex wake model and a shed-vortex sheet wake model are reported. Comparisons with the linear theory of Wagner (1925), the theoretical results associated with the single lumped-vortex wake model and the full wake model are presented. In addition, it is shown that the computational predictions are consistent with results reported by Katz and Plotkin (2001); they applied a distribution of vortices to model the wake. In the present paper the importance of resolving the chordwise pressure distribution in unsteady hydrofoil problems is elucidated. New predictions of both the evolution of lift and induced drag are reported for the instantaneously started flat plate. The computational predictions are compared with theorecticalpredictions also discussed in this paper.

A Two-Dimensional Multibody Integral Approach for Forces in Inviscid Flow With Free Vortices and Vortex Production

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Juan Li ◽  
Chen-Yuan Bai ◽  
Zi-Niu Wu
Keyword(s):  
Flat Plate ◽  
Lift Force ◽  
Vortex Sheet ◽  
Inviscid Flow ◽  
The Body ◽  
Integral Approach ◽  
Two Dimensional ◽  
Middle Point ◽  
Dependent Behavior ◽  
The Individual

In this paper, we propose an integral force approach for potential flow around two-dimensional bodies with external free vortices and with vortex production. The method can be considered as an extension of the generalized Lagally theorem to the case with continuous distributed vortices inside and outside of the body and is capable of giving the individual force of each body in the case of multiple bodies. The lift force formulas are validated against two examples. One is the Wagner problem with vortex production and with moving vortices in the form of a vortex sheet. The other is the lift of a flat plate when there is a standing vortex over its middle point. As a first application, the integral approach is applied to study the lift force of a flat plate induced by a bounded vortex above the plate. This bounded vortex may represent a second small airfoil at incidence. For this illustrative example, the lift force is found to display an interesting distance-dependent behavior: for a clockwise circulation, the lift force acting on the main airfoil is attractive for small distance and repulsive for large distance.

Aerodynamic Analysis and Optimization of Wind Turbines Based on Full Free Vortex Wake Model

2013 ◽  
Author(s):  
Xiancheng Song ◽  
Jiang Chen ◽  
Gang Du ◽  
Lucheng Ji
Keyword(s):  
Wind Turbine ◽  
Series Representation ◽  
Vortex Sheet ◽  
Vortex Wake ◽  
Thrust Coefficient ◽  
Free Vortex ◽  
Aerodynamic Analysis ◽  
Multipole Methods ◽  
Wake Model ◽  
Free Wake

The aerodynamic analysis and optimization of wind turbine based on a full free vortex wake model is presented. Instead of a simplification of the vortex wake structure, this model predict an adequate free-wake extension which can accurately take into account the profound influence of vortex sheet downstream on the aerodynamic performance of wind turbine. The problem that the model suffers from high computational costs is solved by combining the Fast Multipole Methods (FMM) for an efficient evaluation of the Biot–Savart law with the parallel processing. The model is applied to the aerodynamic analysis of wind turbine and a stable convergent numerical solution is achieved using the pseudo-implicit technique (steady) and predictor-corrector PC2B scheme (unsteady). The optimization based on this analysis is also efficiently carried out using a Fourier series representation of the bound circulation as optimization variables, using a given thrust coefficient as a constraint. The chord and twist distributions that completely define the geometry are produced from the obtained optimal bound circulation distribution. The optimization is capable of quickly finding an optimum design using a few optimization variables. The validations of presented methods are performed through comparisons with the National Renewable Energy Laboratory (NREL) wind turbine experiment.

scholarly journals Prandtl–Batchelor flow past a flat plate with a forward-facing flap

1984 ◽  
Vol 143 ◽  
pp. 351-365 ◽  
Author(s):  
P. G. Saffman ◽  
S. Tanveer
Keyword(s):  
Flat Plate ◽  
Leading Edge ◽  
Vortex Sheet ◽  
Inviscid Flow ◽  
The Body ◽  
Two Dimensional ◽  
Rear Edge ◽  
Flow Past ◽  
Range Of Values ◽  
Streamline Method

Two-dimensional steady inviscid flow past an inclined flat plate with a forward-facing flap attached to the rear edge is considered for the case when a vortex sheet separates from the leading edge of the flat plate and reattaches at the leading edge of the flap, with uniform vorticity distributed between the vortex sheet and the body. Solutions are found for a particular geometry and a range of values of the vorticity. The method used to calculate the flow is an extension of a free-streamline method widely used in cases where the velocity is a constant on the separating streamline.

scholarly journals Structural insights into the modulation of PDGF/PDGFR-β complexation by hyaluronan derivatives

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Kanagasabai Balamurugan ◽  
Linda Koehler ◽  
Jan-Niklas Dürig ◽  
Ute Hempel ◽  
Jörg Rademann ◽  
...  
Keyword(s):  
Growth Factor ◽  
Cancer Progression ◽  
Computational Analysis ◽  
Vascular Endothelial ◽  
Receptor Recognition ◽  
Dynamics Simulations ◽  
Endothelial Growth Factor ◽  
Structural Insights ◽  
Important Physiological Process ◽  
Computational Predictions

Abstract Angiogenesis is an important physiological process playing a crucial role in wound healing and cancer progression. Vascular endothelial growth factor (VEGF) and platelet derived growth factor (PDGF) are key players in angiogenesis. Based on previous findings regarding the modulation of VEGF activity by glycosaminoglycans (GAG), here we explore the interaction of hyaluronan (HA)-based GAG with PDGF and its receptor PDGFR-β by applying molecular modeling and dynamics simulations in combination with surface plasmon resonance (SPR). Computational analysis on the interaction of oligo-hyaluronan derivatives with different sulfation pattern and functionalization shows that these GAG interact with PDGF in relevant regions for receptor recognition, and that high sulfation as well as modification with the TAMRA group convey stronger binding. On the other hand, the studied oligo-hyaluronan derivatives are predicted to scarcely recognize PDGFR-β. SPR results are in line with the computational predictions regarding the binding pattern of HA tetrasaccharide (HA4) derivatives to PDGF and PDGFR-β. Furthermore, our experimental results also show that the complexation of PDGF to PDGFR-β can be modulated by HA4 derivatives. The results found open the path for considering HA4 derivatives as potential candidates to be exploited for modulation of the PDGF/PDGFR-β signaling system in angiogenesis and related disease conditions.

Computational Simulations of Dynamic Compaction of Dry Sand

2012 ◽  
Vol 598 ◽  
pp. 516-519
Author(s):  
Yu Qing Ding ◽  
Wen Hui Tang ◽  
Xian Wen Ran ◽  
Xin Xu
Keyword(s):  
Computational Analysis ◽  
Dynamic Compaction ◽  
Back Surface ◽  
Computational Results ◽  
Two Dimensional ◽  
Computational Simulations ◽  
Plate Impact ◽  
Arrival Times ◽  
Dry Sand ◽  
Impact Experiments

The computational analysis of plate impact experiments on dry sand utilizing the Mie- Grüneisen (MG) equation of state and the P-α compaction model were investigated in this study. A number of two dimensional axial symmetric computations were performed by using the hydrocode AUTODYN. The computational results were compared with the particle velocity on the back surface of the rear plate measured by the VISAR system and the first shock-wave arrival times detected by piezoelectric pins in the samples respectively. It was found that the P-α compaction model was more accurately reproduce the experimental data than the MG EOS.

The Effect of Froude Number on Entrainment in Two-Dimensional Line Plumes

1981 ◽  
Vol 103 (3) ◽  
pp. 471-477 ◽  
Author(s):  
W. F. Phillips
Keyword(s):  
Froude Number ◽  
Large Distance ◽  
Universal Constant ◽  
Temperature Profiles ◽  
Two Dimensional ◽  
Development Length ◽  
High Discharge ◽  
Entrainment Coefficient ◽  
Theoretical Results

Theoretical results are presented which predict the entrainment coefficient in a forced plume as a function of the local Froude number. The model does not require any external specification of the velocity and temperature profiles. The Froude number for any plume, in a motionless isothermal ambient, approaches a universal constant, at a large distance above the source. However, it is shown here that the development length for the Froude number, in plumes with high discharge Froude number, is of the order of a few hundred times the discharge width.

scholarly journals Computational analysis of two-dimensional wing aeroelastic flutter using Navier-Stokes model

2018 ◽  
Vol 9 (4) ◽  
pp. 3459-3472 ◽  
Author(s):  
Magdy Saeed Hussin ◽  
Ashraf Ghorab ◽  
Mohamed A. El-Samanoudy
Keyword(s):  
Computational Analysis ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Aeroelastic Flutter

Part II: Steady aerofoil-spoiler characteristics

1987 ◽  
Vol 91 (908) ◽  
pp. 359-366
Keyword(s):  
Separated Flow ◽  
Experimental Results ◽  
Surface Singularity ◽  
Separation Region ◽  
Two Dimensional ◽  
Trailing Edge ◽  
Singularity Method ◽  
Total Head ◽  
Low Speeds ◽  
Theoretical Results

Summary A surface singularity method has been formulated to predict two-dimensional spoiler characteristics at low speeds. Vorticity singularities are placed on the aerofoil surface, on the spoiler surface, on the upper separation streamline from the spoiler tip and on the lower separation streamline from the aerofoil trailing edge. The separation region is closed downstream by two discrete vortices. The flow inside the separation region is assumed to have uniform total head. The downstream extent of the separated wake is an empirical input. The flows both external and internal to the separated regions are solved. Theoretical results have been obtained for a range of spoiler-aerofoil configurations which compare reasonably with experimental results. The model is deficient in that it predicts a higher compression ahead of the spoiler than obtained in practice. Furthermore, there is a minimum spoiler angle below which a solution is not possible; it is thought that this feature is related to the physical observation that at small spoiler angles, the separated flow from the spoiler reattaches on the aerofoil upper surface ahead of the trailing edge.

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