scholarly journals Numerical and Experimental Investigation into the Aerodynamic Benefits of Rotorcraft Formation Flight

2021 ◽  
Author(s):  
Ramon Duivenvoorden ◽  
Mark Voskuijl ◽  
Lars Morée ◽  
Jan de Vries ◽  
Finbar van der Veen
Keyword(s):  
Wind Tunnel ◽  
Numerical Study ◽  
Numerical Models ◽  
Wind Tunnel Experiment ◽  
Numerical Results ◽  
Formation Flight ◽  
Total Power ◽  
Small Scale ◽  
Main Rotor ◽  
Rotor Disk

The use of formation flight to achieve aerodynamic benefit applied to rotorcraft has, unlike its fixed-wing counterpart, received little attention in the literature. This document presents a proof-of-concept of rotorcraft formation flight from two independent investigations: a numerical study of a fully articulated helicopter influenced by an upstream helicopter wake and a wind-tunnel experiment featuring two small-scale helicopter models with fixed-pitch blades. Both cases feature a representation of two helicopters in a diagonal, staggered formation aligned on the advancing side of the main rotor, but do not simulate directly comparable flight conditions. The vertical and lateral alignment of the two helicopters is varied in order to observe the achievable reductions in main rotor power required during cruise flight. The wind-tunnel experiment data yield an estimated maximum total power reduction for the secondary aircraft of approximately 24%, while the numerical models yield reductions between 20% and 34% dependent on flight velocity. Both experiments predict a higher potential for aerodynamic benefit than generally observed for fixed-wing formations, which is attributed to the asymmetric velocity profile induced by the wake of the upstream rotor. Optimal lateral alignment of both experimental and numerical results is found to feature overlap of the rotor disk areas, rather than tip-to-tip alignment, as a result of the circular rotor disk area. Experimental data show an optimal vertical alignment of the secondary rotorcraft below the primary, due to the self-induced vertical displacement of the rotor wake, which is absent from the numerical results due to the application of a flat wake assumption. The results show a promising potential for rotorcraft formation flight, though due to the limited nature of the models used, conclusions cannot be generalized. The potential aerodynamic benefit indicated by the present study invites further research in the field of rotorcraft formation flight.

2D and 3D Multiscale Computational Modeling of Dynamic Microorgan Devices as Drug Screening Platforms

2015 ◽  
Author(s):  
Filippos Tourlomousis ◽  
Robert C. Chang
Keyword(s):  
Large Scale ◽  
Numerical Study ◽  
Numerical Results ◽  
Scale Model ◽  
Small Scale ◽  
Optimum Process ◽  
Shear Stresses ◽  
Enzymatic Reactions ◽  
Modeling Approach

The ability to incorporate three-dimensional (3D) hepatocyte-laden hydrogel constructs using layered fabrication approaches into devices that can be perfused with drugs enables the creation of dynamic microorgan devices (DMDs) that offer an optimal analog of the in vivo liver metabolism scenario. The dynamic nature of such in vitro metabolism models demands reliable numerical tools to determine the optimum process, material, and geometric parameters for the most effective metabolic conversion of the perfused drug into the liver microenvironment. However, there is a current lack of literature that integrates computational approaches to guide the optimum design of such devices. The groundwork of the present numerical study has been laid by our previous study [1], where the authors modeled in 2D an in vitro DMD of arbitrary dimensions and identified the modeling challenges towards meaningful results. These constructs are hosted in the chamber of the microfluidic device serving as walls of the microfluidic array of channels through which a fluorescent drug substrate is perfused into the microfluidic printed channel walls at a specified volumetric flow rate assuring Stokes flow conditions (Re<<1). Due to the porous nature of the hydrogel walls, a metabolized drug product is collected at the outlet port. A rigorous FEM based modeling approach is presented for a single channel parallel model geometry (1 free flow channel with 2 porous walls), where the hydrodynamics, mass transfer and pharmacokinetics equations are solved numerically in order to yield the drug metabolite concentration profile at the DMD outlet. The fluid induces shear stresses are assessed both in 3D, with only 27 cells modeled as single compartment voids, where all of the enzymatic reactions are assumed to take place. In this way, the mechanotransduction effect that alters the hepatocyte metabolic activity is assessed for a small scale model. This approach overcomes the numerical limitations imposed by the cell density (∼1012 cells/m3) of the large scale DMD device. In addition, a compartmentalization technique is proposed in order to assess the metabolism process at the subcellular level. The numerical results are validated with experiments to reveal the robustness of the proposed modeling approach and the necessity of scaling the numerical results by preserving dynamic and biochemical similarity between the small and large scale model.

scholarly journals Numerical Study on Flow Characteristics in a Francis Turbine during Load Rejection

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 716 ◽  
Author(s):  
Daqing Zhou ◽  
Huixiang Chen ◽  
Jie Zhang ◽  
Shengwen Jiang ◽  
Jia Gui ◽  
...  
Keyword(s):  
Geometric Modeling ◽  
Numerical Study ◽  
Numerical Models ◽  
Experimental Testing ◽  
Pressure Fluctuations ◽  
Load Condition ◽  
Numerical Results ◽  
Francis Turbine ◽  
Labyrinth Seals ◽  
Load Rejection Process

Labyrinth seals are not usually included in the numerical models of hydraulic machinery to simplify the geometric modeling, and thereby reduce the calculation burden. However, this simplification affects the numerical results, especially in the load rejection process, because disc friction losses, volume losses, and pressure fluctuations in the seal ring (SR) clearance passage are neglected. This paper addresses the issue by considering all of the geometrical details of labyrinth seals when conducting multiscale flow simulations of a high head Francis turbine under a transient load rejection condition using the commercial software code. A comparison of the numerical results that were obtained with the experimental testing data indicates that the calculated values of both torque and mass discharge rate are 8.65% and 5% slightly less than the corresponding values that were obtained from experimental model testing, respectively. The obtained pressure fluctuations of the Francis turbine in the vaneless zone and the draft tube appear to more closely match with the experimental test data when including SR clearance. Moreover, the flow rates through SR clearance passages were very small, but the pressure fluctuations among them were significantly enhanced under the minimal load condition. The numerical model with SR clearance can more accurately reflect the fact that the water thrust on the runner only fluctuates from 800 N to 575 N during the load rejection process, even though the water thrust on the blades varies from −220 N to 1200 N. Therefore, multiscale flow study is of great significance in understanding the effect of clearance flow on the load rejection process in the Francis turbine.

scholarly journals Numerical Contribution to Airflow Study Through a Generic Merchant Ship Models

2020 ◽  
Vol 15 ◽  
Keyword(s):  
Wind Tunnel ◽  
Numerical Study ◽  
Three Dimensional ◽  
Numerical Results ◽  
Numerical Code ◽  
Generic Models ◽  
Merchant Ship ◽  
Acceleration And Deceleration ◽  
Low Speed Wind Tunnel ◽  
Good Agreement

The merchant ships are continuously recruited by the world meteorological organization (WMO) as Voluntary Observing Ship (VOS) for the collect of meteorological parameters at the ocean surface. VOS meteorological observation includes many parameters such as the wind speed measured by anemometers. This measurement is biased by the presence of ship and superstructure. Little work was carried out in this field. Between them we find the experimental work at a low speed wind tunnel of Southampton University which studies the airflow distortion over simple models (generic models) of VOS merchant ship. This study presents numerical results of a 3D simulation analyzing airflow effect above the bridge of a generic merchant ship models involved in VOS. For this purpose three-dimensional, stationary and turbulent, numerical simulation has been achieved the flow over the bridge of a tanker and a container ship at 1/ 46 scale using a numerical code and CFX code with turbulence k-ε models. This numerical study allows us to know the position of the line of equality as well as the zone of acceleration and deceleration of the flow. The results obtained numerically by numerical code and CFX code are compared with those obtained experimentally in the wind tunnel of Southampton University. Numerical results are in a good agreement with experimental results and can be used as a reference to find the position of the equality line and to know the error range in of the anemometer velocity reading.

Lab-Scale Wind Tunnel Experiment Test of Wind Turbine Blades for Performance Evaluation

2019 ◽  
Author(s):  
Jae Sang Moon ◽  
Sung Soo Park ◽  
Sung Ho Yu ◽  
Sangkyun Kang ◽  
Jang-Ho Lee
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Performance Test ◽  
Turbine Blades ◽  
Wind Tunnel Experiment ◽  
Small Scale ◽  
Wind Turbine Blades ◽  
Speed Test ◽  
Scale Experiment ◽  
Blade Model

Abstract This study evaluates the performance of a HAWT blade model using the lab-scale wind tunnel experiment. The small-scale wind turbine blade model has been designed based on the newly developed airfoil, KA2. A 3-blade rotor, based on the blade model, is tested using the digital wind tunnel. The performance is estimated by measuring the rotor-induced shaft torque. To estimate the performance properly, two different methods have been used depending on the blade rotation speed. Test results are compared with the theoretical estimation by BEM. This study provides the methodology to the performance test of wind turbine blades using lab-scale experiment. Moreover, results represent the applicability of the KA2 airfoil to wind turbine blades.

Numerical study of resonant shallow flows past a lateral cavity: benchmarking the model with a new experimental data set

2020 ◽  
Author(s):  
Adrián Navas-Montilla ◽  
Sergio Martínez-Aranda ◽  
Antonio Lozano ◽  
Pilar García-Navarro
Keyword(s):  
Water Resources ◽  
Shallow Water ◽  
Large Scale ◽  
Numerical Study ◽  
Numerical Results ◽  
Small Scale ◽  
Coupling Mechanism ◽  
Data Set ◽  
Shallow Flows ◽  
Lateral Cavity

&lt;p&gt;Steady shallow flows past an open channel lateral cavity have been widely studied in the last years due to their engineering and environmental relevance, e.g. for river restoration purposes [1]. Such flows can induce the excitation of an eigenmode of a gravity standing wave inside the cavity, called seiche, which may be coupled with the shedding of vortices at the opening of the cavity. A complete understanding of such phenomenon is necessary as it may determine the mass exchange between the main channel and the cavity [2]. A numerical study of the resonant flow in a channel with a single lateral cavity is herein presented. Five different flow configurations at a fixed Froude number (Fr=0.8), measured in the laboratory [3], are used as a benchmark. Such experiments are reproduced using a high-order 2D depth-averaged URANS model based on the shallow water equations, assuming that shallow water turbulence is mainly horizontal [4]. The large-scale horizontal vortices are resolved by the model, whereas the effect of the small-scale turbulence is accounted for by means of a turbulence model. Water surface elevation and velocity measurements are used for comparison with the numerical results. A detailed comparison of the seiche amplitude distribution in the cavity-channel area is presented, showing a good agreement between the numerical results and the observations. Frequency analysis techniques are used to extract the relevant features of the flow. It is evidenced that the proposed model is able to reproduce the observed spatial distribution of oscillation nodes and anti-nodes, as well as the time-averaged flow field. The coupling mechanism between the gravity wave inside the cavity and the unstable shear layer at the opening of the cavity is also accurately captured. &lt;br&gt;&lt;br&gt;&lt;/p&gt;&lt;p&gt;[1] C. Juez, M. Thalmann, A. J. Schleiss &amp; M. J.&amp;#160; Franca, Morphological resilience to flow fluctuations of fine sediment deposits in bank lateral cavities, Advances in Water Resources,&amp;#160; 115 (2018) 44-59.&lt;/p&gt;&lt;p&gt;[2] I. Kimura &amp; T. Hosoda, Fundamental properties of flows in open channels with dead zone, Journal of Hydraulic Engineering 123 (1997) 98-107.&lt;/p&gt;&lt;p&gt;[3] S. Mart&amp;#237;nez-Aranda, J. Fern&amp;#225;ndez-Pato, D. Caviedes-Voulli&amp;#232;me, I. Garc&amp;#237;a-Palac&amp;#237;n &amp; P. Garc&amp;#237;a-Navarro, Towards transient experimental water surfaces: a new benchmark dataset for 2D shallow water solvers, Advances in water resources, 121 (2018) 130-149.&lt;/p&gt;&lt;p&gt;[4] A. Navas-Montilla, C. Juez, M.J. Franca &amp; J. Murillo, Depth-averaged unsteady RANS simulation of resonant shallow flows in lateral cavities using augmented WENO-ADER schemes, Journal of Computational Physics, 24 (2019) 203-217.&lt;/p&gt;

scholarly journals Numerical models development for unidirectional air flow diffusers with lobed and circular orifices

2019 ◽  
Vol 111 ◽  
pp. 01049
Author(s):  
Laurentiu Tacutu ◽  
Ilinca Nastase ◽  
Florin Bode ◽  
Cristiana Croitoru ◽  
Catalin Lungu
Keyword(s):  
Numerical Simulation ◽  
Boundary Conditions ◽  
Numerical Study ◽  
Numerical Models ◽  
Ventilation System ◽  
Numerical Results ◽  
Airflow Distribution ◽  
Numerical Grid ◽  
Computational Resources ◽  
Real Scale

In order to achieve more realistic boundary conditions on the inlet of a ventilation system it is necessary to study the influences of the air diffuser orifices geometry on the airflow distribution in the enclosure. Integrating these orifices directly in a real scale air diffuser for a numerical study will result in a huge computational grid which will translate in huge computational resources and a much larger calculation time. The solution, in this case, was the numerical simulation of the airflow through small parts of the studied air diffuser. Later, the numerical results will be implemented as boundary conditions in the unidirectional diffuser of a numerical simulation that represents a real scale operating room (OR). In the current study two diffusers with different orifices were studied, one having circular („O”) and the other one lobbed („+”) orifices. The initial numerical model had 25 orifices on the diffuser, but because of the very large numerical grid resulted for the initial meshes (>35 million tetrahedral cells), a solution with only 4 orifices was chosen for this study. A mesh independency study was made for these two types of air diffusers. The numerical studies were made using RANS method, with SST k-ω turbulence model in steady state conditions. The numerical results obtained with the first step models showed very good agreement with the PIV stereoscopic experimental measurements.

Using Ansys for Design and Numerical Study of a Specific Fixed Wing UAV

2018 ◽  
Vol 55 (4) ◽  
pp. 652-657 ◽  
Author(s):  
Gabriel Murariu ◽  
Razvan Adrian Mahu ◽  
Adrian Gabriel Murariu ◽  
Mihai Daniel Dragu ◽  
Lucian P. Georgescu ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Unmanned Aerial Vehicle ◽  
Numerical Study ◽  
Flight Time ◽  
Cluster System ◽  
Numerical Results ◽  
Operational Performance ◽  
Gliding Flight ◽  
Aerial Vehicle ◽  
Constant Altitude

This article presents the design of a specific unmanned aerial vehicle UAV prototype own building. Our UAV is a flying wing type and is able to take off with a little boost. This system happily combines some major advantages taken from planes namely the ability to fly horizontal, at a constant altitude and of course, the great advantage of a long flight-time. The aerodynamic models presented in this paper are optimized to improve the operational performance of this aerial vehicle, especially in terms of stability and the possibility of a long gliding flight-time. Both aspects are very important for the increasing of the goals� efficiency and for the getting work jobs. The presented simulations were obtained using ANSYS 13 installed on our university� cluster system. In a next step the numerical results will be compared with those during experimental flights. This paper presents the main results obtained from numerical simulations and the obtained magnitudes of the main flight coefficients.

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