scholarly journals Experimental and computational investigation on interaction between nano rotor and aerodynamic rudder

2019 ◽  
Vol 11 ◽  
pp. 175682931986602
Author(s):  
Dong Yang ◽  
Zhen Liu ◽  
Chen Bu ◽  
Zhao Shanyong
Keyword(s):  
Flow Field ◽  
Deflection Angle ◽  
Aerodynamic Performance ◽  
Computational Investigation ◽  
Thrust Coefficient ◽  
Propulsive Performance ◽  
Propulsion Performance ◽  
Torque Coefficient ◽  
Left And Right ◽  
The Moment

The interference effect between the nano rotor and aerodynamic rudder was studied experimentally and computationally. Propulsive performance of nano rotor and aerodynamic performance of aerodynamic rudder were achieved experimentally. The disturbed flow field of nano rotor was also analyzed computationally to disclose the flow mechanics of the interaction. Results showed that the nano rotor has a great effect on the aerodynamic performance of aerodynamic rudder. The moment of aerodynamic rudder fluctuated with the rotor-to-rudder spacing and achieved the smallest value at the spacing of 0.5R. And the moment of aerodynamic rudder varied with deflection angle linearly. Aerodynamic rudder influenced the propulsion performance of the nano rotor slightly. The thrust coefficient and torque coefficient increased a little with spacing but changed slightly with the deflection angle. Numerical simulation showed that aerodynamic rudder blocked the flow field of the nano rotor and the counterclockwise rotation of the rotor drives the flow in the downstream rotating in a counterclockwise direction resulting in the different angle of attack between left and right rudder surface.

An Investigation Into the Effect of Biofouling on Full-Scale Propeller Performance Using CFD

2019 ◽  
Author(s):  
Soonseok Song ◽  
Yigit Kemal Demirel ◽  
Mehmet Atlar
Keyword(s):  
Open Water ◽  
Full Scale ◽  
Roughness Effect ◽  
Thrust Coefficient ◽  
Propulsion Performance ◽  
Negative Effect ◽  
Precise Prediction ◽  
Torque Coefficient ◽  
Open Water Performance ◽  
Propeller Performance

Abstract The negative effect of biofouling on ship resistance has been investigated since the early days of naval architecture. However, for more precise prediction of fuel consumption of ships, understanding the effect of biofouling on ship propulsion performance is also important. In this study, CFD simulations for the full-scale performance of KP505 propeller in open water, including the presence of marine biofouling, were conducted. To predict the effect of barnacle fouling on the propeller performance, experimentally obtained roughness functions of barnacle fouling were employed in the wall-function of the CFD software. The roughness effect of barnacles of varying sizes and coverages on the propeller open water performance was predicted for advance coefficients ranging from 0.2 to 0.8. From the simulations, drastic effects of barnacle fouling on the propeller open water performance were found. The result suggests that the thrust coefficient decreases while the torque coefficient increases with increasing level of surface fouling, which leads to a reduction of the open water efficiency of the propeller. Further investigations into the roughness effect on the pressure and velocity field, surface pressure and wall shear stress, and propeller vortices were examined.

An Experimental Study of Compressible Flow Through Convergent-Conical Nozzles, Including a Comparison With Theoretical Results

1972 ◽  
Vol 94 (4) ◽  
pp. 926-930 ◽  
Author(s):  
R. L. Thornock ◽  
E. F. Brown
Keyword(s):  
Flow Field ◽  
Pressure Ratio ◽  
Internal Flow ◽  
Thrust Coefficient ◽  
Local Flow ◽  
Flow Angle ◽  
Propulsive Performance ◽  
Nozzle Shape ◽  
Flow Through ◽  
Theoretical Results

Despite the widespread use of convergent-conical nozzles as propulsion nozzles in turbojet aircraft, little attention has been given to the effect of nozzle shape on their propulsive performance. This paper presents the results of an experimental investigation in which the effect of nozzle angle on the internal characteristics of the flow field and on the propulsive performance of convergent conical nozzles was investigated. In addition, a theoretical solution is described which was developed as a part of this investigation. Fifteen, twenty-five, and forty-degree nozzles were tested at pressure ratios from 1.4 to 7.0. Measurements were made of the nozzle discharge coefficient, thrust coefficient, local flow angle, and wall static pressure. The properties of the internal flow field were seen to be affected by the nozzle angle and at pressure ratios less than the choked pressure ratio by the pressure ratio as well. The results of the theoretical analysis substantiate this behavior and are in reasonable agreement with the experimental data.

scholarly journals Design and Experimental Study of an Over-Under TBCC Exhaust System

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Jianwei Mo ◽  
Jinglei Xu ◽  
Liuhuan Zhang
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Exhaust System ◽  
Aerodynamic Performance ◽  
Combined Cycle ◽  
Mode Transition ◽  
Jet Streams ◽  
Thrust Coefficient ◽  
Transition Mode ◽  
Exhaust Jet

Turbine-based combined-cycle (TBCC) propulsion systems have been a topic of research as a means for more efficient flight at supersonic and hypersonic speeds. The present study focuses on the fundamental physics of the complex flow in the TBCC exhaust system during the transition mode as the turbine exhaust is shut off and the ramjet exhaust is increased. A TBCC exhaust system was designed using methods of characteristics (MOC) and subjected to experimental and computational study. The main objectives of the study were: (1) to identify the interactions between the two exhaust jet streams during the transition mode phase and their effects on the whole flow-field structure; (2) to determine and verify the aerodynamic performance of the over–under TBCC exhaust nozzle; and (3) to validate the simulation ability of the computational fluid dynamics (CFD) software according to the experimental conditions. Static pressure taps and Schlieren apparatus were employed to obtain the wall pressure distributions and flow-field structures. Steady-state tests were performed with the ramjet nozzle cowl at six different positions at which the turbine flow path were half closed and fully opened, respectively. Methods of CFD were used to simulate the exhaust flow and they complemented the experimental study by providing greater insight into the details of the flow field and a means of verifying the experimental results. Results indicated that the flow structure was complicated because the two exhaust jet streams interacted with each other during the exhaust system mode transition. The exhaust system thrust coefficient varied from 0.9288 to 0.9657 during the process. The CFD simulation results agree well with the experimental data, which demonstrated that the CFD methods were effective in evaluating the aerodynamic performance of the TBCC exhaust system during the mode transition.

scholarly journals Research on the Performance of Pumpjet Propulsor of Different Scales

2022 ◽  
Vol 10 (1) ◽  
pp. 78
Author(s):  
Jun Yang ◽  
Dakui Feng ◽  
Liwei Liu ◽  
Xianzhou Wang ◽  
Chaobang Yao
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Fluid Dynamic ◽  
Open Water ◽  
Small Scale ◽  
Thrust Coefficient ◽  
Total Thrust ◽  
Torque Coefficient ◽  
Open Water Performance ◽  
Thrust And Torque

This study presents a numerical research on the open-water performance of a pumpjet propulsor at different scales. Simulations were performed by an in-house viscous CFD (Computational Fluid Dynamic) code. The Reynolds-averaged Navier–Stokes (RANS) method with SST k-w turbulence model is employed. A dynamic overset grid is used to treat the relative motion between the rotor and other parts. The numerical results are compared with the model test data and they agree well. Comparisons for the open-water performance between the pumpjet propulsors with two scales are carried out. The results indicate that the total thrust coefficient of the large-scale pumpjet propulsor is greater than that of the small-scale one while the torque coefficient is smaller. Therefore, the efficiency of the large-scale pumpjet propulsor is about 8~10% higher than that of the small-scale pumpjet propulsor. The open-water performance of the rotor, pre-swirl stator and duct is obtained separately to estimate the discrepancies on the thrust and torque coefficients between different scales. To analyze the scale effect from different parts, the research on flow field and pressure distribution are carried out. The variation of total thrust and torque coefficient comes mainly from the rotor, which is caused by the flow field, influenced by the duct and stator.

scholarly journals Hues of Color Afterimages

i-Perception ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 204166952090355 ◽  
Author(s):  
Jan Koenderink ◽  
Andrea van Doorn ◽  
Christoph Witzel ◽  
Karl Gegenfurtner
Keyword(s):  
Iterative Method ◽  
Fixation Mark ◽  
Narrow Region ◽  
Left And Right ◽  
The Moment ◽  
Color Circle ◽  
The Relationship ◽  
Method Of Adjustment

We studied the relationship between color afterimages and complementary colors. The hues of afterimages of 24 inducer hues, uniformly distributed over the rgb color circle, were measured by an iterative method of adjustment. The judgment of equality of hue of the afterimage and a synthesized patch was effectively judged at the moment immediately after the switch-off of the inducer, when the synthesized patch went through any number of iterative adjustments. The two patches—both phenomenally present, but only one optically presented—appeared to the left and right of a fixation mark that was fixated throughout the whole procedure. Thus, both patches were present in eccentric vision. The hues of afterimages were found to be quite different from the hue of the complementary of the inducer. Almost one half of the color circle (orange to chartreuse) leads to afterimage hues in a narrow region of purples. This implies that color circles based on diametrically opposed inducer–afterimage hues are necessarily inconsistent. Yet, perhaps surprisingly, the relation between primary and afterimage hues is still approximately an involution (they are reciprocally related).

scholarly journals Hydrodynamic Analysis of Self-Propulsion Performance of Wave-Driven Catamaran

2021 ◽  
Vol 9 (11) ◽  
pp. 1221
Author(s):  
Weixin Zhang ◽  
Ye Li ◽  
Yulei Liao ◽  
Qi Jia ◽  
Kaiwen Pan
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Dynamic Model ◽  
Dynamic Structure ◽  
Ocean Waves ◽  
Static State ◽  
Small Surface ◽  
Propulsion Performance ◽  
Multi Body ◽  
Body Dynamic

The wave-driven catamaran is a small surface vehicle driven by ocean waves. It consists of a hull and hydrofoils, and has a multi-body dynamic structure. The process of moving from static state to autonomous navigation driven by ocean waves is called “self-propulsion”, and reflects the ability of the wave-driven catamaran to absorb oceanic wave energy. Considering the importance of the design of the wave-driven catamaran, its self-propulsion performance should be comprehensively analysed. However, the wave-driven catamaran’s multi-body dynamic structure, unpredictable dynamic and kinematic responses driven by waves make it difficult to analyse its self-propulsion performance. In this paper, firstly, a multi-body dynamic model is established for wave-driven catamaran. Secondly, a two-phase numerical flow field containing water and air is established. Thirdly, a numerical simulation method for the self-propulsion process of the wave-driven catamaran is proposed by combining the multi-body dynamic model with a numerical flow field. Through numerical simulation, the hydrodynamic response, including the thrust of the hydrofoils, the resistance of the hull and the sailing velocity of the wave-driven catamaran are identified and comprehensively analysed. Lastly, the accuracy of the numerical simulation results is verified through a self-propulsion test in a towing tank. In contrast with previous research, this method combines multi-body dynamics with computational fluid dynamics (CFD) to avoid errors caused by artificially setting the motion mode of the catamaran, and calculates the real velocity of the catamaran.

Experimental study on axially non-uniform clearances in a linear turbine cascade with a cavity squealer tip

2018 ◽  
Vol 233 (5) ◽  
pp. 1645-1655
Author(s):  
Shaowen Chen ◽  
Qinghe Meng ◽  
Weihang Li ◽  
Zhihua Zhou ◽  
Songtao Wang
Keyword(s):  
Flow Field ◽  
Buffer Zone ◽  
Aerodynamic Performance ◽  
Field Structure ◽  
Tip Clearance ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Passage Vortex ◽  
Flow Loss

The effects of axially non-uniform clearances on the tip leakage flow and aerodynamic performance in a linear turbine cascade with a cavity squealer tip were investigated in this study with the objective of improving the flow loss and tip flow field structure. A calibrated five-hole probe was used for the measurement of three-dimensional flows downstream of the cascade. The method of oil-flow visualization was used to show the endwall flow field structure. The distribution of endwall static pressure was measured particularly by using the special moveable endwall. The axially non-uniform clearance, as a novel strategy that has a non-negligible influence on tip clearance flow and clearance leakage loss, may become a potential technology for improving aerodynamic performance in turbine cascades. By using the expanding clearance, the flow loss at the outlet is reduced effectively and an apparent improvement of aerodynamic performance in the turbine cascade is gained. Under the tip clearances of 0.75% H and 2% H, the maximum reduction of overall total pressure loss coefficient at the outlet is separately about 2.3% and 3.5% compared with the uniform clearance. The shrinkage of the buffer zone is considered to be able to weaken the interaction of the tip leakage vortex and passage vortex and thus reduce the loss of passage vortex. For the shrinking clearance, a noticeable decline in the aerodynamic performance of turbine cascade with cavity squealer tip is exhibited at both on and off design conditions in contrast to the uniform clearance. In addition, the effects of axially non-uniform clearances on the aerodynamic performance at off-design conditions have been investigated.

Influence of the pressure relief door area and aspect ratio on discharge and force characteristics

2019 ◽  
Vol 92 (2) ◽  
pp. 107-116
Author(s):  
Shiyu Feng ◽  
Chenchen Wang ◽  
Xiaotian Peng ◽  
Yan Yan ◽  
Yang Deng ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Discharge Coefficient ◽  
Geometric Parameters ◽  
Pressure Relief ◽  
Thrust Coefficient ◽  
Content Type ◽  
Moment Coefficient ◽  
The Moment ◽  
Compartment Pressures ◽  
Force Characteristics

Purpose The purpose of this paper is to analyze the effects of the PRD geometric parameters, including the area and aspect ratio, on the discharge and force characteristics of pressure relief process under various plenum compartment pressures and Mach numbers. Design/methodology/approach Under various plenum compartment pressures and Mach numbers, the effect of the area and aspect ratio on the discharge and force characteristics of the PRD are numerically investigated via a three-dimensional steady Reynolds-averaged Navier–Stokes equations solver based on structured grid technology. Findings When the aspect ratio remains constant, the discharge coefficient CD, thrust coefficient CT and moment coefficient CM are not affected by the PRD. When the area is constant, the aspect ratio dramatically impacts the discharge and force characteristics because the aspect ratio increases, the discharge coefficient CD of the PRD decreases, and the thrust coefficient CT and the moment coefficient CM both increase. When the aspect ratio is 2, the discharge coefficient CD decreases by 14.7 per cent, the thrust coefficient CT increases by 10-15 per cent, and the moment coefficient CM increases by 10-23 per cent compared with when the aspect ratio is 1. Practical implications This study provides detailed data and conclusions for nacelle PRD researchers and actual engineering applications. Originality/value On the basis of considering the influence of operating conditions on the discharge and force characteristics of the nacelle PRD, the impact of geometric parameters, including the area and aspect ratio on the discharge and force characteristics is comprehensively considered.

Computational Fluid Dynamics Study of a Flexible Flapping Hydrofoil Propulsor

2016 ◽  
Author(s):  
Harikrishnan Vijayakumaran ◽  
Parameswaran Krishnankutty
Keyword(s):  
Fluid Dynamics ◽  
Reynolds Number ◽  
Strouhal Number ◽  
Thrust Coefficient ◽  
Number Range ◽  
Wake Field ◽  
Propulsive Performance ◽  
Velocity Magnitude ◽  
Maximum Angle ◽  
Motion Parameters

A CFD study to understand the hydrodynamics and fluid flow around a chordwise flexible hydrofoil with combined sway and yaw motion which imitates the caudal fin flapping in thunniforms, is presented. The dependency of motion parameters of the flexible flapping hydrofoil to its propulsive performance is studied by carrying out the analyses over a Strouhal number range of 0.1 to 0.4 in steps of 0.025 at three maximum angle of attacks viz. 10°,15°,20°. Qualitative observations of the wake field and trailing jet is presented using velocity magnitude contours and vorticity contours. The analyses carried out at 40,000 Reynolds number and sway amplitude of 0.75 chordlength, revealed that the average thrust coefficient increases with increase in Strouhal number and maximum angle of attacks. The highest efficiency is achieved when the maximum angle of attack is 15° and Strouhal number is 0.225.

The effect analysis of an engine jet on an aircraft blast deflector

2018 ◽  
Vol 41 (4) ◽  
pp. 990-1001
Author(s):  
Song Ma ◽  
Jianguo Tan ◽  
Xiankai Li ◽  
Jiang Hao
Keyword(s):  
High Temperature ◽  
Flow Field ◽  
High Speed ◽  
Deflection Angle ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Aircraft Engine ◽  
Experimental Results ◽  
Exhaust Gases ◽  
The Impact

This paper establishes a novel mathematical model for computing the plume flow field of a carrier-based aircraft engine. Its objective is to study the impact of jet exhaust gases with high temperature, high speed and high pressure on the jet blast deflector. The working condition of the nozzle of a fully powered on engine is first determined. The flow field of the exhaust jet is then numerically simulated at different deflection angle using the three-dimensional Reynolds averaged Navier–Stokes equations and the standard [Formula: see text]-[Formula: see text] turbulence method. Moreover, infra-red temperature tests are further carried out to test the temperature field when the jet blast deflector is at the [Formula: see text] deflection angle. The comparison between the simulation results and the experimental results show that the proposed computation model can perfectly describe the system. There is only 8–10% variation between them. A good verification is achieved. Moreover, the experimental results show that the jet blast deflector plays an outstanding role in driving the high-temperature exhaust gases. It is found that [Formula: see text] may be the best deflection angle to protect the deck and the surrounding equipment effectively. These data results provide a valuable basis for the design and layout optimization of the jet blast deflector and deck.

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