scholarly journals Experimental Study to Quantify the Rotor-to-Rotor Interaction Characteristics of a Small Unmanned-Aerial-Vehicle

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Wenwu Zhou ◽  
Zhe Ning ◽  
Hui Hu
Keyword(s):  
Noise Level ◽  
Open Space ◽  
Separation Distance ◽  
Recirculation Region ◽  
Piv Measurements ◽  
Aeroacoustic Noise ◽  
Baseline Case ◽  
Flow Interactions ◽  
Aerial Vehicle ◽  
Twin Rotor

The flow interactions between laterally aligned rotors were investigated experimentally to study the rotor-to-rotor interactions on the aerodynamic and aeroacoustic performance of small unmanned aerial vehicles (UAVs). Two identical rotors, similar to the dimensions of Phantom 3 (DJI), were mounted separately on different stages in a wide-open space. High-accuracy force and sound measurements were conducted to document the thrust and noise at various separation distances. The detailed flow structures and corresponding vortex evolutions behind the rotors were resolved clearly by using high-resolution PIV measurements. As the rotor separation distance decreased, intensified flow interactions were noted within the rotors. More specifically, the twinrotor with separation distance of L= 0.05D exhibited a significantly enhanced thrust fluctuation (i.e., ~ 240% higher) and augmented noise level (i.e., ~ 3dB) in comparison with that of baseline case. Measured PIV results indicated that a strong recirculation region existed near the top-right of the twin-rotor case, which is believed to be the reason for the increased thrust fluctuations and aeroacoustic noise level.

On the Turbulent Flow Downstream of a Partly Opened Throttle Valve

1994 ◽  
Vol 208 (4) ◽  
pp. 213-222
Author(s):  
T-F Hu ◽  
Y-Y Hsu
Keyword(s):  
Boundary Layer ◽  
Turbulent Flow ◽  
Three Dimensional ◽  
Recirculation Region ◽  
Jet Stream ◽  
Hot Wire ◽  
Inlet Pipe ◽  
Wall Boundary Layer ◽  
Throttle Valve ◽  
Flow Interactions

Experimental measurements were performed in a model inlet pipe on the turbulent flow downstream of the throttle valve of a commercial motorcycle carburettor. The inlet pipe was made of a section of straight plexiglass tube to facilitate the access of hot-wire and pressure probes. Continuous dry air was drawn into the model to establish the flow. The flow downstream of the partly opened throttle valve is found composed of a recirculation region, a three-dimensional jet stream and a wall boundary layer. Complex turbulent flow interactions among the recirculation region, the jet stream and the boundary layer are observed. This study clearly demonstrates that the jet stream, which includes a major portion of the flow going downstream, shows similarity of axial velocity profiles on planes normal to the angular direction.

PIV Measurements in a Confined Jet

2002 ◽  
Author(s):  
A. Shinneeb ◽  
J. D. Bugg ◽  
R. Balachandar
Keyword(s):  
Free Surface ◽  
Velocity Field ◽  
Surface Flow ◽  
Recirculation Region ◽  
Maximum Deviation ◽  
Centerline Velocity ◽  
Upward Flow ◽  
Piv Measurements ◽  
Exit Velocity ◽  
The Mean

This paper reports PIV measurements made at three locations in an axisymmetric, confined jet that is approaching a free surface from below. The apparatus consists of a tank 40.5 cm × 40.5 cm at its base and 61 cm high. A 9 mm diameter nozzle is centered in the base of the tank and directs a jet of water upwards. The jet produced has a top-hat velocity profile with a maximum deviation of 0.32% of the mean and an axial relative turbulence intensity of 0.60%. The water is removed from the tank by an overflow around the perimeter of the tank. The PIV measurements achieved a spatial resolution of between 0.425–1.08 mm. The measurements show details of the velocity field in three regions of the flow; at the jet exit, near the surface on the centerline of the jet, and near the top corner of the tank. The centerline velocity remains at the exit velocity until ≈5D from the exit. The axial confinement of the jet begins to significantly influence the centerline velocity at ≈13D from the free surface. All entrained fluid is deflected downward from the horizontal surface flow as it approaches the overflow around the perimeter of the tank. This creates a large recirculation region in the upper region of the tank driven by the downward flow along the wall and the upward flow of the jet itself at the center of the tank.

scholarly journals Analysis of Traffic Noise in Taman Kota Lumintang Denpasar

2019 ◽  
Vol 10 (02) ◽  
pp. 20585-20591
Author(s):  
Adrian Pradana ◽  
I Made Tamba ◽  
I Ketut Widnyana
Keyword(s):  
Noise Level ◽  
Open Space ◽  
Direct Method ◽  
Traffic Noise ◽  
Ground Level ◽  
Quality Standard ◽  
Sound Level ◽  
The Road ◽  
Level Meter ◽  
City Park

This research was conducted to analyze the level of traffic noise in Lumintang City Park, Denpasar. The measurement method is by using a direct method that is using an integrating sound level meter that has an LTMS measurement facility, namely Leq with a measuring time every 5 seconds. The examination is carried out by measuring for 10 minutes. The measurement time is carried out during the 24 hour activity (NGO) on December 3, 2018. The measurement distance ranges from 5-10 meters from the road, with a height of 1-1.2 m from the ground level. The results of the research on the level of traffic noise in Lumintang City Park Denpasar showed the noise level that exceeded the noise level quality standards of the green open space area of 50 dB, where in the first lane the traffic noise level was 92.52 dB at L3. While the noise research in lane 2 shows that the highest traffic noise level of 85.70 dB occurs at L5. For day and night (NGO) noise levels in lane 1 amounting to 70.13 dB and lane 2 of 67.95 dB has exceeded the quality standard of green open space, so that it can cause physical and psychological disturbances for visitors to the Taman Lumintang City of Denpasar..

scholarly journals Pengendalian Kebisingan Dari Aktivitas Penerbangan di Lingkungan Sekitar Bandara Sultan Thaha Jambi dengan Pemanfaatan Ruang Terbuka Hijau

2021 ◽  
Vol 4 (1) ◽  
pp. 25
Author(s):  
Nur Sodiq ◽  
G M Saragih ◽  
Peppy Herawati
Keyword(s):  
Noise Level ◽  
Open Space ◽  
Noise Exposure ◽  
Quality Standard ◽  
Residential Area ◽  
Noise Levels ◽  
Populated Area ◽  
Forest Park ◽  
Operational Activities ◽  
Natural Barrier

Noise is a sound pollution and its existence is undesirable in a certain level and time, which has the potential to cause human health problems and environmental comfort. One of the causes of noise levels is due to airport operational activities, from landing to take off. For this reason, it is necessary to control the noise around the Sultan Thaha Jambi airport area, by utilizing green open space as a barrier that can reduce noise levels. This study aims to determine the level of airport noise in certain zones and evaluate the existence of green open space (RTH) whether it is appropriate to become a natural barrier as a barrier to reduce noise caused by flight activities from Sultan Thaha Jambi airport. The results showed the noise level dB (A) from flight activities in each zone, namely the lowest in zones 1 and 3, amounting to 52.08 dB (A), and the highest in zone 5 at 87.93 dB (A). , while the existence of Green Open Space (RTH) is only in zone 1, and 3 are forest park areas, and fields around the Sultan Thaha Jambi airport area, so the existence of this Green Open Space (RTH) is able to reduce noise levels by 2.11 dB (A) based on KEP-48 / MNLH / 11/1996 the quality standard of the allowable noise level is 50 dB (A). While zone 5 is a residential area, the noise level figure is quite high, namely 87.93 dB (A), due to the densely populated area, lack of green open space (RTH), and proximity to motorized vehicle transportation activities, and adjacent to the runway. runway airport. However, not all activities are carried out continuously. So that the residential area is still feasible if exposed to noise exposure either from airport activities or other activities.

Corner Separation Dynamics in a Linear Compressor Cascade

2016 ◽  
Author(s):  
Gherardo Zambonini ◽  
Xavier Ottavy ◽  
Jochen Kriegseis
Keyword(s):  
Three Dimensional ◽  
Recirculation Region ◽  
Spanwise Direction ◽  
Compressor Cascade ◽  
Linear Compressor ◽  
Time Resolved ◽  
Piv Measurements ◽  
Blade Section ◽  
Pod Analysis ◽  
Linear Compressor Cascade

This paper considers the inherent unsteady behavior of the three dimensional separation in the corner region of a subsonic linear compressor cascade equipped of thirteen NACA 65-009 profile blades. Detailed experimental measurements were carried out at different sections in spanwise direction achieving, simultaneously, unsteady wall pressure signals on the surface of the blade and velocity fields by time-resolved PIV measurements. Two configurations of the cascade were investigated with an incidence of 4° and 7°, both at Re = 3.8 * 105 and Ma = 0.12 at the inlet of the facility. The intermittent switch between the two statistical preferred sizes of separation, large and almost suppressed, is called bimodal behaviour. The existence of such oscillation, reported at first in previous experimental and numerical works on the same test rig, is confirmed for both incidences. Additionally, the present PIV measurements provide, for the first time, time-resolved flow visualizations of the size switch of the separation with an extended field of view covering the entire blade section. The interaction of random large structures of the incoming boundary layer with the blade is found to be a predominant element that destabilizes the separation boundary. The recirculation region enlarges when these high vorticity perturbations blend with larger eddies situated in the aft part of the blade. Such massive separation persists until the blockage in the passage causes the breakdown of the largest structures in the aft part of the blade. The flow starts again to accelerate and the separation is almost suppressed. Finally, POD analysis is carried out to decompose flow modes and to contribute to the clarification of underlying cause-effect-relations, which predominate the dynamics of the present flow scenario.

Influence of Main Stage Air Splits on the Ignition Performance of TeLESS-II Combustor

2017 ◽  
Author(s):  
Xiaotong Mi ◽  
Chi Zhang ◽  
Bo Wang ◽  
Yuzhen Lin
Keyword(s):  
Flow Field ◽  
Air Flow ◽  
Pollutant Emissions ◽  
Recirculation Region ◽  
Stable Operation ◽  
Inlet Temperature ◽  
Main Stage ◽  
Fuel Distribution ◽  
Baseline Case ◽  
The Impact

The centrally staged layout is preferred in the advanced aero-engine combustor to achieve low pollutant emissions as well as stable operation in lean premixed prevaporized combustion. However, because the high-speed main stage airflow prevents the pilot fuel droplets arriving at igniter tip and has a strong convection effect on the initial flame kernel, the application of centrally staged combustor is restricted by its poor ignition and lean blow-out performance. In the centrally staged combustor, the main stage and pilot stage have strong coupled influences on the flow field and fuel distribution. The aim of this paper is to research the impact of the main stage air split on the ignition performance for the baseline case and the comparison case of the main swirler in the TeLESS-II combustor. The main stage air flow rate of the comparison case is about 8 percent less than that of the baseline case. The results of the ignition test at room inlet temperature and pressure indicate that the ignition performance of the comparison case is significantly better than that of the baseline case. The results of the lean blow-out tests show that the main stage air splits do not make the lean blow-out performance worse. To achieve a better understanding of the test results, PLIF technology and CFD analysis were used to measure the fuel distribution and non-reacting flow field. The PLIF and CFD results demonstrate that the most of the fuel spray disperse outward into the main stage cold airflow in the baseline case so that the pilot flame is hard to be established, which leads to poor ignition performance. On the other hand, in the comparison case, the most of the fuel is confined in the recirculation region, which gives a better ignition performance. Compared with the baseline case, the main stage airflow velocity decays faster in the comparison case. It changes the direction of the instantaneous velocity in the spark vicinity, which makes it more likely for the ignition kernel to be captured by the recirculation stream in the comparison case. Therefore, the different fuel distribution and flow field characteristics cause the ignition performance improvement in the comparison case. The improvement is due to the different main stage air flow rates, which is the consequence of the main stage air split.

Komfort akustyczny w open space w narracji projektantów

2017 ◽  
Vol 2 (52) ◽  
pp. 61-70
Author(s):  
Anita Basińska ◽  
Agnieszka Jeran
Keyword(s):  
Human Resources ◽  
Working Conditions ◽  
Noise Level ◽  
Open Space ◽  
Human Resources Management ◽  
Work Place ◽  
Office Work ◽  
Resources Management ◽  
Good Working ◽  
Design Solutions

Nowadays a significant amount of work is office work. How it is performed is determined by both applied techniques of human resources management and organization of workspace; both these factors relate to each other. The increasing importance of good working conditions, as well as effectiveness, lead to serious discussions about the importance of comfort in a work place. Because the most popular type of workspace is open space, we have analyzed design solutions to provide comfort to employees. We have analyzed 50 projects published on the site sztukawnetrza.pl, and then we classified and described methods and means that reduce noise in open space.It has also caught our attention that in Poland there seems to be no objective acoustic indicators clearly defining the accepted noise level. This indicates the absence of such narration among designers though it does not mean such standards are not applied.

A Novel Fixed Twin-Rotor Unmanned Aerial Vehicle with Variable Angle Louver Rudder

2021 ◽  
Author(s):  
Yixin Zhang ◽  
Jianfeng Zhou ◽  
Shaoping Wang ◽  
Mengqi Yang ◽  
Shaoshi Li
Keyword(s):  
Unmanned Aerial Vehicle ◽  
Variable Angle ◽  
Aerial Vehicle ◽  
Twin Rotor

scholarly journals Effect of the Backward Facing Step on a Transverse Jet in Supersonic Crossflow

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4170 ◽  
Author(s):  
Jincheng Zhang ◽  
Zhenguo Wang ◽  
Mingbo Sun ◽  
Hongbo Wang ◽  
Chaoyang Liu ◽  
...  
Keyword(s):  
Large Scale ◽  
Separation Bubble ◽  
Step Height ◽  
Recirculation Region ◽  
Mixing Efficiency ◽  
Spanwise Direction ◽  
Backward Facing Step ◽  
Jet Mixing ◽  
Transverse Jet ◽  
Baseline Case

A transverse jet in the supersonic crossflow is one of the most promising injection schemes in scramjet, where the control or enhancement of jet mixing is a critical issue. In this paper, the effect of the backward facing step on the characteristics of jet mixing was investigated by three-dimensional large eddy simulation (LES). The simulation in the flat plate configuration (step height of 0) was performed as the baseline case to verify the computation framework. The distribution of the velocity and pressure obtained by the LES agreed well with the experiment, which shows the reliability of the LES code. Then, two steps with a height of 1.0D and 1.58D (D is the injector diameter) were numerically compared to the non-step baseline case. The comparison of the three cases illustrates the effect of the large-scale recirculation region on the variable distribution, and shock and vortex structures in the flow field. In the windward region, the shear layers become thicker, and the convection velocity of the shear vortexes reduces. In the leeward region, the wake vortices almost disappear while the counterrotating vortex pairs (CVPs) expand in the spanwise direction. In the area upstream of the jet, the separation bubble works with the upstream large-scale recirculation zone to entrain the jet into the upstream near-wall zone. At last, a comparison of the overall mixing performance of the three cases revealed that the penetration depth and mixing efficiency increased with the step height increasing.

Sign in / Sign up

Export Citation Format

Share Document