scholarly journals Quadrotor Drone Hovering in Ground Effect

2021 ◽  
Vol 33 (2) ◽  
pp. 339-347
Author(s):  
Yasutada Tanabe ◽  
Hideaki Sugawara ◽  
Shigeru Sunada ◽  
Koichi Yonezawa ◽  
Hiroshi Tokutake ◽  
...  
Keyword(s):  
Ground Effect ◽  
Flow Fields ◽  
Velocity Profiles ◽  
High Fidelity ◽  
Variable Pitch ◽  
Rotating Speed ◽  
Flow Recirculation ◽  
Total Thrust

A variable-pitch-controlled quadrotor drone was simulated in the ground effect using a high-fidelity CFD solver. In contrast to a single rotor in the ground effect, which has been extensively studied for conventional helicopters, the flow fields around multiple rotors are complex. In this study, the rotating speed of the rotors was maintained constant, and the blade pitch angles were adjusted so that the total thrust of the multicopter was the same regardless of the rotor height from the ground. It was observed that the power required for the quadrotors, which generate the same thrust, decreases when the rotors are approaching the ground from the height where they can be considered to be out of the ground effect, but increases locally when the rotor height is approximately the rotor radius, owing to flow recirculation into the rotor, and then decreases abruptly when the rotors further approach the ground. The outwash from the quadrotors depends heavily on the direction relative to the quadrotor layout. Along the plane crossing the diagonal rotor centers, the outwash velocity profiles resemble those of a single rotor; however, the outwash from the rotor gaps is stronger and extends to a much higher altitude.

An Experimental Investigation of Flow Fields Within Miniature Scale Centrifugal Pumps

2006 ◽  
Author(s):  
D. Kearney ◽  
J. Punch ◽  
R. Grimes
Keyword(s):  
Centrifugal Pump ◽  
Characteristic Curve ◽  
Flow Fields ◽  
Velocity Profiles ◽  
Heat Fluxes ◽  
Model Verification ◽  
Air Cooling ◽  
Centrifugal Pumps ◽  
Test Bed ◽  
Forced Air

Thermal management has become a key point in the development of contemporary electronics systems. It is evident that heat fluxes are currently approaching the limits of conventional forced air cooling, and that liquid technologies are now under consideration. The objective of this paper is to investigate the flow fields within a miniature scale centrifugal pump in order to determine velocity profiles describing the flow. The experimental setup consisted of a hydrodynamic test bed constructed to measure the pressure-flow characteristic of a centrifugal pump with a rated volumetric flow of 9 l/min. The impeller diameter of the pump under consideration was 34.3mm, and the characterisation experiments were carried out at a constant impeller speed. Particle-Image Velocimetry (PIV) was used to measure velocity profiles within the volute section of the pump. Synchronised velocity profiles are illustrated for three operating points on the pump characteristic curve. A hydrodynamic analysis of the velocity vectors at the impeller tip is also included, and pump model verification is then discussed based on the comparison between the theoretical predictions and the PIV data.

Effect of Rotating Speed on Performance of Electrical Submersible Pump

2019 ◽  
Author(s):  
Yang Yang ◽  
Ling Zhou ◽  
Weidong Shi ◽  
Chuan Wang ◽  
Wei Li ◽  
...  
Keyword(s):  
Flow Field ◽  
Current Trend ◽  
Performance Testing ◽  
Flow Fields ◽  
Computational Domain ◽  
Submersible Pump ◽  
Data Set ◽  
Rotating Speed ◽  
Compact Size ◽  
Electrical Submersible Pump

Abstract High speed rotating pump is the current trend in pump’s development and application, which has the advantages of compact size and energy-saving features. The electrical submersible pump, typically called an ESP, is an efficient and reliable artificial-lift method for lifting moderate to high volumes of fluids from wellbores, which have been wildly used for oil or groundwater extraction. To verify the similarity of pump performance under different rotating speeds, a typical ESP is selected as the model pump. By employing the numerical simulation and performance testing methods, the external performance characteristics and internal flow fields under different rotating speeds of the pump are studied. The entire computational domain is established by two stages ESP, and then meshed with the high-quality structured grid based on the Q-type and Y-type block topology. Grid sensitivity analysis is carried out to determine the appropriate mesh density for mesh independent solution. SST k-ω turbulence model with standard wall function in conjunction with Reynolds-Averaged Navier-Stokes (RANS) equations is used to solve the steady flow field. The results show that the increase in the rotating speed could increase the ESP’s head significantly. ESP’s external characteristics under different speeds meet the similar conversion rule quite well. In addition, the flow field distributions in the main flow components of the pump have great similarity at different rotating speeds. The experimental test results for a prototype show good agreement with the simulation results, including the pump’s head, efficiency and axial force. This paper provides a data set for further understanding of the effects of rotating speeds on ESP’s performance and inner flow fields.

scholarly journals A numerical investigation into electroosmotic flow in microchannels with complex wavy surfaces

2011 ◽  
Vol 15 (suppl. 1) ◽  
pp. 87-94 ◽  
Author(s):  
Her-Terng Yau ◽  
Cheng-Chi Wang ◽  
Ching-Chang Cho ◽  
Cha’o-Kuang Chen
Keyword(s):  
Cross Sections ◽  
Electroosmotic Flow ◽  
Flow Characteristics ◽  
Velocity Profiles ◽  
Governing Equations ◽  
Electrical Field ◽  
Flow Recirculation ◽  
Wavy Surfaces ◽  
Pressure Driven Flow ◽  
General Method

This study investigates the flow characteristics of electroosmotic flow in a microchannel with complex wavy surfaces. A general method of coordinate transformation is used to solve the governing equations describing the electroosmotic flow in the microchannel. Numerical simulations are performed to analyze the effects of wave amplitude on the electrical field, flow streamlines, and flow fields in the microchannel. The simulation results show that, compared to a traditional pressure-driven flow, flow recirculation is not developed in the electroosmotic flow in a microchannel with complex wavy surfaces. The simulations also show that the electrical field and velocity profiles change along the channel in the region of wavy surfaces. Non-flat velocity profiles are observed in different cross-sections of the channel in the region of wavy surfaces.

A Framework of Multi-Fidelity Topology Design and its Application to Optimum Design of Flow Fields in Battery Systems

2019 ◽  
Author(s):  
Kentaro Yaji ◽  
Shintaro Yamasaki ◽  
Shohji Tsushima ◽  
Kikuo Fujita
Keyword(s):  
Topology Optimization ◽  
Design Optimization ◽  
Optimization Problem ◽  
Optimization Problems ◽  
Flow Fields ◽  
Design Solution ◽  
Design Parameters ◽  
High Fidelity ◽  
Topology Optimization Problem ◽  
Battery Systems

Abstract We propose a novel framework based on multi-fidelity design optimization for indirectly solving computationally hard topology optimization problems. The primary concept of the proposed framework is to divide an original topology optimization problem into two subproblems, i.e., low- and high-fidelity design optimization problems. Hence, artificial design parameters, referred to as seeding parameters, are incorporated into the low-fidelity design optimization problem that is formulated on the basis of a pseudo-topology optimization problem. Meanwhile, the role of high-fidelity design optimization is to obtain a promising initial guess from a dataset comprising topology-optimized design candidates, and subsequently solve a surrogate optimization problem under a restricted design solution space. We apply the proposed framework to a topology optimization problem for the design of flow fields in battery systems, and confirm the efficacy through numerical investigations.

A Numerical Investigation of Blood Damage in the Hinge Area of BMHV

2010 ◽  
Author(s):  
Jingshu Wu ◽  
Anna Fallon ◽  
Helene Simon ◽  
Cyrus Aidun ◽  
Ajit Yoganathan
Keyword(s):  
Heart Valves ◽  
Cardiac Cycle ◽  
Three Dimensional ◽  
Flow Fields ◽  
High Fidelity ◽  
Thromboembolic Complications ◽  
Hemodynamic Effects ◽  
Flow Properties ◽  
Blood Damage ◽  
Blood Elements

Bileaflet mechanical heart valves (BMHVs) have been widely used to replace native valves. Unfortunately, the design of bileaflet MHVs produces flow fields that may cause damage to blood elements, especially at the hinge area. The objectives of this study are to analyze the flow properties around the hinge area and through the valve, to further understand the cause of blood damage and provide improved designs to reduce the adverse hemodynamic effects of valves that cause platelet activation and damage blood elements. An important part of this improvement is to understand the hemodynamic effects produced by different valve designs, and how the surrounding flow fields affect thromboembolic formation. The hemodynamics of the valve flow is characterized by complex spatial and temporal three-dimensional structures that arise from the pulsatility of the flow, the complexity of the geometry and the flow-dependent motion of the valve leaflets. High fidelity simulations of the valve flow fields throughout the cardiac cycle is required to improve and refine existing valve designs so as to ultimately develop bileaflet MHVs with minimal thromboembolic complications.

Helicopter encounters with aircraft vortex wakes

2001 ◽  
Vol 105 (1043) ◽  
pp. 1-8 ◽  
Author(s):  
G. D. Padfield ◽  
G. P. Turner
Keyword(s):  
Ground Effect ◽  
Performance Standard ◽  
Rational Approach ◽  
High Fidelity ◽  
Case Scenario ◽  
Worst Case ◽  
Safety Issues ◽  
Control Power ◽  
Simultaneous Operations ◽  
Safety Cases

Abstract This paper presents the results of a study into wake vortex-related safety issues associated with simultaneous rotary and fixed-wing aircraft operations at busy airports. An analysis conducted using both simple analytic models and high fidelity FLIGHTLAB simulations has considered a helicopter located in the hover above the landing point and during approach and landing. Tip vortices from a Boeing 747 are shed and are assumed to be travelling in a horizontal plane by the time they reach the helicopter. A worst case scenario is simulated, with no vortex ageing or attenuation due to ground effect. Both simple and high fidelity simulations indicate that the rates of climb and descent induced by the vortex tails can be significant. When the helicopter flies through the vortex core, moderately large transient excursions in attitude occur within a few seconds. When the helicopter does not pass through or close to the core, while the flight path perturbations are still significant, the attitude response is shown to be significantly reduced. The predicted cyclic control power required to counteract the vortex-induced hub moments is about 40% of full control, compared with more than 100% for an ‘equivalent’ fixed-wing aircraft. The control power required in the vertical, collective, axis to overcome the downdraught and updraught in the vortex tails can be as high as 15–20%. While the authors have not tried to make judgements as to whether pilots would find the transients manageable, an approach to quantifying the extent of the hazard has been suggested using the failure transients criteria from the handling qualities performance standard ADS–33. Combined with analysis of the likelihood of such occurrences at particular airports, such response criteria offer a rational approach to developing safety cases for simultaneous operations.

On two-dimensional laminar wakes and jets

1969 ◽  
Vol 39 (1) ◽  
pp. 163-172 ◽  
Author(s):  
Karl K. Chen
Keyword(s):  
Initial Velocity ◽  
Flow Fields ◽  
Velocity Profiles ◽  
Two Dimensional ◽  
Spatial Stability ◽  
The Past ◽  
Stable Solutions ◽  
Similar Solutions ◽  
Laminar Wakes ◽  
Surrounding Fluid

The flow fields in two-dimensional, isoenergetic, viscous free mixing with constant β and with initial velocity profiles deviating slightly from those given by wakelike solutions of the Falkner-Skan equation for that β are considered. The similar solutions of the Falkner-Skan equation are investigated in more detail than in the past, e.g. we show that as β → −1 the flows approach the pure jet with the surrounding fluid at rest, and that there are new branch solutions for β < −1. We have investigated the spatial stability of these flows; it is found that for β > − 0·5 the only spatially stable solutions are the trivial ones f′(η) ≡ 1, but for −1 < β < − 0·5 there are non-trivial, jet-like solutions which are spatially stable. As to the new branch solutions for β < − 1, all are spatially unstable.

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