A multi-fidelity modelling approach for evaluation and optimization of wing stroke aerodynamics in flapping flight

2013 ◽  
Vol 721 ◽  
pp. 118-154 ◽  
Author(s):  
Lingxiao Zheng ◽  
Tyson L. Hedrick ◽  
Rajat Mittal
Keyword(s):  
Parameter Space ◽  
Computational Models ◽  
Computational Modelling ◽  
Element Model ◽  
Flapping Wing ◽  
Navier Stokes ◽  
Specific Flow ◽  
Wing Stroke ◽  
Modelling Approach ◽  
Blade Element

AbstractThe aerodynamics of hovering flight in a hawkmoth (Manduca sexta) are examined using a computational modelling approach which combines a low-fidelity blade-element model with a high-fidelity Navier–Stokes-based flow solver. The focus of the study is on understanding the optimality of the hawkmoth-inpired wingstrokes with respect to lift generation and power consumption. The approach employs a tight coupling between the computational models and experiments; the Navier–Stokes model is validated against experiments, and the blade-element model is calibrated with the data from the Navier–Stokes modelling. In the first part of the study, blade-element and Navier–Stokes modelling are used concurrently to assess the predictive capabilities of the blade-element model. Comparisons between the two modelling approaches also shed insights into specific flow features and mechanisms that are lacking in the lower-fidelity model. Subsequently, we use blade-element modelling to explore a large kinematic parameter space of the flapping wing, and Navier–Stokes modelling is used to assess the performance of the wing-stroke identified as optimal by the blade-element parameter survey. This multi-fidelity optimization study indicates that even within a parameter space constrained by the animal’s natural flapping amplitude and frequency, it is relatively easy to synthesize a wing stroke that exceeds the aerodynamic performance of the hawkmoth wing stroke. Within the prescribed constraints, the optimal wing stroke closely approximates the condition of normal hover, and the implications of these findings on hawkmoth flight capabilities as well as on the issue of biomimetic versus bioinspired design of flapping wing micro-aerial vehicles, are discussed.

Yaw Aerodynamics Analyzed With Three Codes in Comparison With Experiment

2003 ◽  
Author(s):  
Helge Aagaard Madsen ◽  
Niels N. So̸rensen ◽  
Scott Schreck
Keyword(s):  
Element Model ◽  
Navier Stokes ◽  
Local Flow ◽  
Flow Angle ◽  
Comparison With Experiment ◽  
Actuator Disc ◽  
Grid Points ◽  
Yaw Angle ◽  
Angle Interval ◽  
Blade Element

Yaw aerodynamics were computed with three codes of different complexity; 1) The 3D Navier Stokes solver Ellipsys3D using 5–8 million grid points; 2) HAWC3D which is a 3D actuator disc model coupled to a blade element model and using 20–30.000 grid points and 3) HAWC, a finite element based aeroelastic code using The Blade Element Momentum (BEM) model for the aerodynamics. Simulations were performed for two experiments. The first is the field rotor measurements on a 100 kW turbine at Risoe where local flow angle (LFA) and local relative velocity (LRV) at one radial station have been measured in a yaw angle interval of ±60°. The other experiment is the NREL measurements on a 10 m rotor in the NASA Ames 80 ft × 120 ft wind tunnel. LFA were measured at five radial stations and data for the 45° yaw case were analyzed. The measured changes in LFA caused by the yawing were used as the main parameter in the comparison with the models. In general a good correlation was found comparing the Ellipsys3D results with the LFA measured on the NREL rotor whereas a systematic underestimation of the amplitude in LFA as function of azimuth was observed for the two other models. This could possibly be ascribed to upwash influence on the measured LFA.

Calculation of Carotid Artery Flow Rates Using Doppler Ultrasound: Implications of Velocity Profile Skewing

2012 ◽  
Author(s):  
Jonathan P. Mynard ◽  
David A. Steinman
Keyword(s):  
Carotid Artery ◽  
Velocity Profile ◽  
Doppler Ultrasound ◽  
Computational Models ◽  
Peak Velocity ◽  
Computational Modelling ◽  
Carotid Bifurcation ◽  
Sample Volume ◽  
Patient Specific ◽  
Specific Flow

Doppler ultrasound (DUS) is a non-invasive means of obtaining patient-specific flow boundary conditions in computational modelling studies [1] or estimating volumetric flow in clinical studies [2, 3]. To convert velocity information to a flow waveform, three related assumptions are often applied, 1) that the peak velocity lies in the centre of a cylindrical vessel, 2) that a centrally-located sample volume will thus detect the peak velocity, and 3) that the velocity profile is fully-developed and axisymmetric, being well-approximated by a parabolic (Poiseuille) or Womersley profile. These assumptions may not always be valid, however, even for nominally straight vessels like the common carotid artery (CCA) [4, 5]. While one might expect that flow estimated from DUS would become increasingly inaccurate as the profile becomes less axisymmetric, the scale of such errors and their relation to the true profile shape have not been quantified for the CCA. Moreover, for a heavily skewed velocity profile, the peak velocity may not lie within the DUS sample volume, and hence the choice of sample volume or beam-vessel orientation may also affect the accuracy of flow calculations. In this study, we investigate these issues by performing an idealized virtual DUS on data from image-based computational models of the carotid bifurcation.

Computational Modelling of Sloshing in Liquefied Natural Gas Tank

2017 ◽  
Author(s):  
Shen Yang Foong ◽  
Yuting Jin ◽  
Shuhong Chai ◽  
Christopher Chin ◽  
Hayden Marcollo
Keyword(s):  
Natural Gas ◽  
Computational Modelling ◽  
Pressure Profile ◽  
Liquefied Natural Gas ◽  
Computational Method ◽  
Navier Stokes ◽  
Impulsive Loads ◽  
2D And 3D ◽  
Made In ◽  
Modelling Approach

Sloshing in the tank of liquefied natural gas (LNG) carriers has recently attracted immense attention due to the rise in demand for LNG transportation. It occurs in partially filled tanks and is capable of inflicting severe damage to the tank’s interior. One effective method to dampen sloshing activities is by introducing baffles into the tank. In this paper, the nature of sloshing has been investigated using finite volume based unsteady Reynolds Averaged Navier-Stokes (URANS) method. Good correlation was achieved between the results obtained from the presented computations and past studies, demonstrating the feasibility of the established numerical modelling approach. Employing similar computational method, two-dimensional (2D) sloshing computations were performed for different baffle additions at varying filling levels. Observations were made in the baffled tanks where an increase in the number of baffles would cause the sloshing activities to magnify if the baffle height was significantly lower than the filling level. When comparing the 2D and 3D computational results, close resemblance of the average pressure profile and maximum impulsive loads had suggested that 2D simulations are feasible to model sloshing induced loads in a 3D tank.

scholarly journals Gut inference: A computational modelling approach

2021 ◽  
pp. 108152
Author(s):  
Ryan Smith ◽  
Ahmad Mayeli ◽  
Samuel Taylor ◽  
Obada Al Zoubi ◽  
Jessyca Naegele ◽  
...  
Keyword(s):  
Computational Modelling ◽  
Modelling Approach

Replication of left ventricular haemodynamics with a simple planar mitral valve model

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Anna Daub ◽  
Jochen Kriegseis ◽  
Bettina Frohnapfel
Keyword(s):  
Mitral Valve ◽  
Computational Models ◽  
Vortex Formation ◽  
Flow Characteristics ◽  
Left Ventricular ◽  
Computational Effort ◽  
Type Model ◽  
Diastolic Phase ◽  
Valve Model ◽  
Modelling Approach

AbstractTools for the numerical prediction of haemodynamics in multi-disciplinary integrated heart simulations have to be based on computational models that can be solved with low computational effort and still provide physiological flow characteristics. In this context the mitral valve model is important since it strongly influences the flow kinematics, especially during the diastolic phase. In contrast to a 3D valve, a vastly simplified valve model in form of a simple diode is known to be unable to reproduce the characteristic vortex formation and unable to promote a proper ventricular washout. In the present study, an adaptation of the widely used simplest modelling approach for the mitral valve is employed and compared to a physiologically inspired 3D valve within the same ventricular geometry. The adapted approach shows enhanced vortex formation and an improved ventricular washout in comparison to the diode type model. It further shows a high potential in reproducing the main flow characteristics and related particle residence times generated by a 3D valve.

A computational modelling approach to human-elephant interactions in the Bunda District, Tanzania

2021 ◽  
Vol 443 ◽  
pp. 109449
Author(s):  
Abel Ansporthy Mamboleo ◽  
Crile Doscher ◽  
Adrian Paterson
Keyword(s):  
Computational Modelling ◽  
Modelling Approach

Forced Response Assessment Using Modal Force Based Indicator Functions

2008 ◽  
Author(s):  
M. Vahdati ◽  
C. Breard ◽  
G. Simpson ◽  
M. Imregun
Keyword(s):  
Finite Element ◽  
Structural Model ◽  
Stokes Equations ◽  
Linear Time ◽  
Response Assessment ◽  
Element Model ◽  
Forced Response ◽  
Navier Stokes ◽  
Modal Force ◽  
Indicator Functions

This paper will focus on core-compressor forced response with the aim to develop two design criteria, the so-called chordwise cumulative modal force and heightwise cumulative force, to assess the potential severity of the vibration levels from the correlation between the unsteady pressure distribution on the blade’s surface and the structural modeshape. It is also possible to rank various blade designs since the proposed criterion is sensitive to changes in both unsteady aerodynamic loads and the vibration modeshapes. The proposed methodology was applied to a typical core-compressor forced response case for which measured data were available. The Reynolds-averaged Navier-Stokes equations were used to represent the flow in a non-linear time-accurate fashion on unstructured meshes of mixed elements. The structural model was based on a standard finite element representation from which the vibration modes were extracted. The blade flexibility was included in the model by coupling the finite element model to the unsteady flow model in a time-accurate fashion. A series of numerical experiments were conducted by altering the stator wake and using the proposed indicator functions to minimize the rotor response levels. It was shown that a fourfold response reduction was possible for a certain mode with only a minor modification of the blade.

scholarly journals Aspects of Uncertainty Analysis for Large Nonlinear Computational Models

2010 ◽  
Vol 24-25 ◽  
pp. 25-41 ◽  
Author(s):  
Keith Worden ◽  
W.E. Becker ◽  
Manuela Battipede ◽  
Cecilia Surace
Keyword(s):  
Finite Element ◽  
Monte Carlo ◽  
Computational Models ◽  
Element Model ◽  
Finite Element Models ◽  
Bayesian Algorithm ◽  
Basic Principles ◽  
Structure Interaction ◽  
Output Uncertainty ◽  
Input Uncertainties

This paper concerns the analysis of how uncertainty propagates through large computational models like finite element models. If a model is expensive to run, a Monte Carlo approach based on sampling over the possible model inputs will not be feasible, because the large number of model runs will be prohibitively expensive. Fortunately, an alternative to Monte Carlo is available in the form of the established Bayesian algorithm discussed here; this algorithm can provide information about uncertainty with many less model runs than Monte Carlo requires. The algorithm also provides information regarding sensitivity to the inputs i.e. the extent to which input uncertainties are responsible for output uncertainty. After describing the basic principles of the Bayesian approach, it is illustrated via two case studies: the first concerns a finite element model of a human heart valve and the second, an airship model incorporating fluid structure interaction.

A Conceptual Model of Flapping-Wing Mechanism Inspired from the Results of Numerical Study

2013 ◽  
Vol 397-400 ◽  
pp. 783-788
Author(s):  
Xing Wei Zhang ◽  
Chao Wang ◽  
Hang Liu
Keyword(s):  
Conceptual Model ◽  
Power Efficiency ◽  
Stokes Equations ◽  
Numerical Study ◽  
Flapping Wing ◽  
Numerical Results ◽  
Navier Stokes ◽  
Active Deformation ◽  
Navier Stokes Equations ◽  
Wing Model

This paper investigates the aerodynamic forces of several plunging wing models by means of computational fluid dynamics. A finite volume method was used to solve the two-dimensional unsteady incompressible Navier-Stokes equations. The forces and power efficiency have been calculated and compared between sets of different models. Current work found that the nonsymmetrical moving can enhance the lift and thrust forces. The numerical results also prove that the flexible wing model can be use to improve the efficiency and reduce the input. Additionally, a new conceptual model for flapping wing mechanism with active deformation and adaptive nonsymmetrical driving motion is proposed base on the numerical results.

scholarly journals A Neurocomputational Theory of Nightmares: The role of formal properties of nightmare images

2021 ◽  
Author(s):  
Patrick McNamara ◽  
Wesley J Wildman ◽  
George Hodulik ◽  
David Rohr
Keyword(s):  
Individual Difference ◽  
Parameter Space ◽  
Computational Models ◽  
Computational Simulation ◽  
Time Varying ◽  
Individual Difference Variables ◽  
Image Characteristics ◽  
Nightmare Disorder ◽  
Formal Properties

Abstract Study Objectives To test and extend Levin & Nielsen’s (2007) Affective Network Dysfunction (AND) model with nightmare disorder (ND) image characteristics, and then to implement the extension as a computational simulation, the Disturbed Dreaming Model (DDM). Methods We used AnyLogic V7.2 to computationally implement an extended AND model incorporating quantitative effects of image characteristics including valence, dominance, and arousal. We explored the DDM parameter space by varying parameters, running approximately one million runs, each for one month of model time, varying pathway bifurcation thresholds, image characteristics, and individual-difference variables to quantitively evaluate their combinatory effects on nightmare symptomology. Results The DDM shows that the AND model extended with pathway bifurcations and image properties is computationally coherent. Varying levels of image properties we found that when nightmare images exhibit lower dominance and arousal levels, the ND agent will choose to sleep but then has a traumatic nightmare, whereas, when images exhibit greater than average dominance and arousal levels, the nightmares trigger sleep-avoidant behavior, but lower overall nightmare distress at the price of exacerbating nightmare effects during waking hours. Conclusions Computational simulation of nightmare symptomology within the AND framework suggests that nightmare image properties significantly influence nightmare symptomology. Computational models for sleep and dream studies are powerful tools for testing quantitative effects of variables affecting nightmare symptomology and confirms the value of extending the Levin & Nielsen AND model of disturbed dreaming/ND.

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