scholarly journals Coupled Fluid-Thermal Investigation on Drag and Heat Reduction of a Hypersonic Spiked Blunt Body with an Aerodisk

Aerospace ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 19
Author(s):  
Bing Fan ◽  
Jie Huang
Keyword(s):  
Heat Flux ◽  
Drag Reduction ◽  
Stagnation Temperature ◽  
Total Drag ◽  
Coupled Method ◽  
Loosely Coupled ◽  
Fluid Field ◽  
Structural Temperature ◽  
Relative Errors ◽  
Spiked Models

In the traditional investigations on the drag and heat reduction of hypersonic spiked models, only the aerodynamic calculation is performed, and the structural temperature cannot be obtained. This paper adopted the loosely coupled method to study its efficiency of drag and heat reduction, in which the feedback effect of wall temperature rise on aeroheating is considered. The aeroheating and structural temperature were obtained by the CFD and ABAQUS software respectively. The coupling analysis of the hypersonic circular tube was carried out to verify the accuracy of the fluid field, the structural temperature, and the coupled method. Compared with experimental results, the calculated results showed that the relative errors of stagnation heat flux and stagnation temperature were 1.34% and 4.95% respectively, and thus the effectiveness of the coupled method was verified. Installing a spike reduced the total drag of the forebody. The spiked model with an aerodisk reduced the aeroheating of the forebody, while the model without an aerodisk intensified the aeroheating. The spiked model with a planar aerodisk had the best performance on drag and heat reduction among all the models. In addition, increasing the length of the spike reduced the drag and temperature of the forebody. With the increase of the length, the change rates of drag, pressure, heat flux, and temperature decreased gradually. Increasing the diameter of the aerodisk also reduced the temperature of the forebody, while the efficiency of forebody drag reduction first increased and then decreased. In conclusion, the heat and drag reduction must be considered comprehensively for the optimal design of the spike.

scholarly journals Resistance reduction on trimaran ship model by biopolymer of eel slime

2015 ◽  
Vol 12 (2) ◽  
pp. 95-102
Author(s):  
Y. Yanuar ◽  
G. Gunawan ◽  
M. A. Talahatu ◽  
R. T. Indrawati ◽  
A. Jamaluddin
Keyword(s):  
Drag Reduction ◽  
Frictional Resistance ◽  
Skin Surface ◽  
Fish Skin ◽  
Total Drag ◽  
Towing Tank ◽  
Ship Model ◽  
Resistance Reduction ◽  
Towing Tank Test ◽  
Tank Test

Resistance reduction in ship becomes an important issue to be investigated. Energy consumption and its efficiency are related toward drag reduction. Drag reduction in fluid flow can be obtained by providing polymer additives, coating, surfactants, fiber and special roughness on the surface hull. Fish skin surface coated with biopolymers viscous fluid (slime) is one method in frictional resistance reduction. The aim of this is to understanding the effect of drag reduction using eel slime biopolymer in unsymmetrical trimaran ship model. The Investigation was conducted using towing tank test with variation of velocity. The dimension of trimaran model are L = 2 m, B = 0.20 m and T = 0.065 m. The ship model resistance was precisely measured by a load cell transducer. The comparison of resistance on trimaran ship model coated and uncoated by eel slime are shown on the graph as a function of the total drag coefficient and Froude number. It is discovered the trimaran ship model by eel slime has higher drag reduction compared to trimaran with no eel slime at similar displacement. The result shows the drag reduction about 11 % at Fr 0.35.

Transonic wing flutter predictions by a loosely-coupled method

2012 ◽  
Vol 58 ◽  
pp. 45-62 ◽  
Author(s):  
Xiang Zhao ◽  
Yongfeng Zhu ◽  
Sijun Zhang
Keyword(s):  
Coupled Method ◽  
Loosely Coupled ◽  
Wing Flutter

Compact Algebraic Asymptotes for Small and Large Time Surface Temperatures for Regular Solid Bodies Heated With Uniform Heat Flux: Scrutiny of New Critical Fourier Numbers

2020 ◽  
Vol 13 (3) ◽  
Author(s):  
Agustín M. Delgado-Torres ◽  
Antonio Campo ◽  
Yunesky Masip-Macia
Keyword(s):  
Heat Flux ◽  
Large Time ◽  
Small Time ◽  
Uniform Heat Flux ◽  
Dimensionless Time ◽  
Time Approximation ◽  
Surface Temperatures ◽  
Uniform Heat ◽  
Relative Errors ◽  
Solid Bodies

Abstract The alternate infinite series at “small time” have been used to analyze the time variation of surface temperatures (ϕs) in regular solid bodies heated with uniform heat flux. In this way, compact algebraic asymptotes are successfully retrieved for ϕs in a plate, cylinder, and sphere in the “small time” sub-domain extending from 0 to the critical dimensionless time or critical Fourier number. For the “large time” sub-domain, the exact solution is approximated in two ways: with the “one-term” series and with the simple asymptotes corresponding to extreme “large time” conditions. Maximum relative errors of 1.23%, 6.24%, and 0.96% in ϕs for the plate, cylinder, and sphere are τcr obtained, respectively, with the “small time”—“large time” approximation using a traditional approach to fix the τcr value. An alternative approach to set the τcr is proposed to minimize the maximum relative error of the approximated solutions so that values of 1.19%, 3.93%, and 0.16% are then obtained for the plate, cylinder, and sphere, respectively, with the “small time”—“large time” approximation. For the “small time”—“one-term” approximation maximum relative errors of 0.024%, 1.33%, and 0.004% for the plate, cylinder, and sphere are obtained, respectively, with this approach.

Flow Over Two Circular Disks in Tandem

1980 ◽  
Vol 102 (1) ◽  
pp. 104-111 ◽  
Author(s):  
T. Morel ◽  
M. Bohn
Keyword(s):  
Drag Reduction ◽  
Steady Flow ◽  
Unsteady Flows ◽  
Flow Regimes ◽  
Diameter Ratio ◽  
Bluff Bodies ◽  
Steady Flows ◽  
Near Wake ◽  
Total Drag ◽  
Circular Disks

Placing two or more bluff-bodies in tandem is known to lead, in some cases, to configurations with relatively low overall drag. The present study concerns one particular case where two disks of unequal diameters, normal to the flow, are placed in tandem for the purpose of drag reduction. It shows that very significant drag reductions may be achieved by proper sizing of the disk diameters and of the gap between them. Placing a properly sized disk at an optimum distance ahead of a single reference disk can result in a configuration whose total drag is up to 81 percent lower than that of the reference disk alone. If the additional disk is placed behind into the near-wake of the reference disk, the drag of the two-disk configuration can be up to 70 percent lower than for the reference disk alone. Four different flow regimes have been identified, depending on the diameter ratio of the two disks, two with relatively steady flows and two with unsteady flows. The absolute drag minimum was found to occur in one of the two steady-flow regimes.

scholarly journals CFD Study of the Impact of Variable Cant Angle Winglets on Total Drag Reduction

Aerospace ◽  
2018 ◽  
Vol 5 (4) ◽  
pp. 126 ◽  
Author(s):  
Joel Guerrero ◽  
Marco Sanguineti ◽  
Kevin Wittkowski
Keyword(s):  
Fluid Dynamics ◽  
Drag Reduction ◽  
Fuel Efficiency ◽  
Aerodynamic Performance ◽  
Fuel Saving ◽  
Sweep Angle ◽  
Total Drag ◽  
Induced Drag ◽  
Aircraft Performance ◽  
The Impact

Winglets are commonly used drag-reduction and fuel-saving technologies in today’s aviation. The primary purpose of the winglets is to reduce the lift-induced drag, therefore improving fuel efficiency and aircraft performance. Traditional winglets are designed as fixed devices attached at the tips of the wings. However, because they are fixed surfaces, they give their best lift-induced drag reduction at a single design point. In this work, we propose the use of variable cant angle winglets which could potentially allow aircraft to get the best all-around performance (in terms of lift-induced drag reduction), at different angle-of-attack values. By using computational fluid dynamics, we study the influence of the winglet cant angle and sweep angle in the performance of a benchmark wing at a Mach number of 0.8395. The results obtained demonstrate that by carefully adjusting the cant angle, the aerodynamic performance can be improved at different angles of attack.

Exploring Self-Correlation in Flux–Gradient Relationships for Stably Stratified Conditions

2006 ◽  
Vol 63 (11) ◽  
pp. 3045-3054 ◽  
Author(s):  
P. Baas ◽  
G. J. Steeneveld ◽  
B. J. H. van de Wiel ◽  
A. A. M. Holtslag
Keyword(s):  
Heat Flux ◽  
Stability Parameter ◽  
Lapse Rate ◽  
Physical Processes ◽  
Obukhov Length ◽  
Flux Gradient ◽  
Stable Conditions ◽  
Measurement Uncertainties ◽  
Relative Errors ◽  
The Stability

Abstract In this paper, the degree of scatter in flux–gradient relationships for stably stratified conditions is analyzed. It is generally found that scatter in the dimensionless lapse rate ϕh is larger than in the dimensionless shear ϕm when plotted versus the stability parameter z/Λ (where Λ is the local Obukhov length). Here, this phenomenon is explained to be a result of self-correlation due to the occurrence of the momentum and the heat flux on both axes, measurement uncertainties, and other possibly relevant physical processes left aside. It is shown that the ratio between relative errors in the turbulent fluxes influences the orientation of self-correlation in the flux–gradient relationships. In stable conditions, the scatter in ϕm is largely suppressed by self-correlation while for ϕh this is not the case (vice versa for unstable stratification). An alternative way of plotting is discussed for determining the slope of the linear ϕm function.

Tangential Gas Injection Into a Supersonic Stream

2010 ◽  
Author(s):  
Eduard B. Vasilevskiy ◽  
Ivan V. Ezhov ◽  
Andrey V. Novikov
Keyword(s):  
Heat Flux ◽  
Free Stream ◽  
Numerical Study ◽  
Gas Injection ◽  
Angle Of Attack ◽  
Supersonic Stream ◽  
Stagnation Temperature ◽  
Mass Rate ◽  
Free Stream Mach Number ◽  
Injection Effect

An experimental and numerical study of a tangential gas injection effect on a flow pattern and heat flux was carried out. The cooling gas (air) was injected in the flow (air) through the tangential axis-symmetric slot on the spherically blunted cylinder streamlined longitudinally. Experiments were conducted in TsAGI shock wind tunnel at free-stream Mach number M∞ = 6, Reynolds number Re∞, Rw = 0.76×106 (calculated for free-stream parameters and bluntness radius Rw = 37.5 mm), cylinder angle of attack α = 0…30°, slot width h* = hk/Rw = 0–0.021, free-stream stagnation temperature T0 = 710 K, pressure behind the normal shock ps = 0.5 bar. The mass rate of the injected gas G* = gj/πρ∞u∞rw2 = 0…0.12. It is shown, that maximum of the heat flux toward the sphere surface could be sufficiently decreased. For example, for coolant mass rate G* = 0.03 and angle of attack α = 0 the heat flux maximum is reduced by factor of two.

Effect of Riblets Geometry on Drag Reduction

2012 ◽  
Author(s):  
Ekhlas M. Fayyadh ◽  
Nibras M. Mahdi
Keyword(s):  
Drag Reduction ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Turbulent Regime ◽  
Governing Equations ◽  
Navier Stokes Equations ◽  
Total Drag ◽  
Surface Models ◽  
Smooth Model ◽  
Riblet Surface

The effect of longitudinal riblet surface models (U, V and semi-Circular and U with fillet corner riblets) on the performance of unsymmetrical airfoil NACA23015 which has been investigated numerically and experimentally. Numerical investigation involve examining drag reduction by solving the governing equations (Continuity and Navier-Stokes equations) using the known package FLUENT in turbulent regime with appropriate turbulence model (κ-ε). Also measurement in experimental work will be carried out. The results indicate that the riblet surface models are the key parameters for controlling the boundary layer characteristics. The most effective riblet surface is U-riblet with fillet model (Mo.4, h = 0.1mm), by compare to smooth model, the results show a small increment in lift slope curve about 9% and total drag decrease 12% over the angles of attack range from (0° to 17°).

scholarly journals Effect of Shroud Hole on the Force Characteristics of a Circular Cylinder

2019 ◽  
Vol 9 (1) ◽  
pp. 5929-5935
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Circular Cylinder ◽  
Drag Reduction ◽  
Air Flow ◽  
Flow Speed ◽  
Diameter Ratio ◽  
Total Drag ◽  
Lift And Drag ◽  
Force Characteristics

Characteristics of flow pass a shrouded cylinder were investigated experimentally using uniform and non-uniform hole shrouds. The experiments were performed to compare the effect of hole-uniformity of the perforated shroud on the cylinder lift and drag. The porosity for uniform hole shrouds in triangular and square configurations were set around 0.30, while that for non-uniform hole shrouds were set from 0.25 to 0.37. The diameter ratio between the shroud and the bare cylinder was set at 2.0. The experiment was performed in a wind tunnel at Reynolds Number of 9.345 x 103 based on the bare cylinder diameter and constant incoming air flow speed. Results showed that although all shrouded cylinder models reduced drag significantly in comparison to that of the bare cylinder case, the non-uniform hole shrouds were considerably effective than the uniform hole shrouds. Total drag reduction achieved by the non-uniform hole shrouds of 30% porosity was between 90-95% whereas that of uniform hole was only 55-80% at the same porosity.

Partial Cavitation as Drag Reduction Technique and Problem of Active Flow Control

2003 ◽  
Vol 40 (03) ◽  
pp. 181-188
Author(s):  
Eduard Amromin ◽  
Igor Mizine
Keyword(s):  
Drag Reduction ◽  
Flow Control ◽  
Active Flow Control ◽  
Total Drag ◽  
Reduction Techniques ◽  
Partial Cavitation ◽  
Wide Range ◽  
Hull Design ◽  
Successful Employment ◽  
Active Flow

Partial cavitation can substantially reduce the ship total drag in a wide range of her speed. Vented partial cavitation manifested certain advantages in comparison with other drag reduction techniques. Its successful employment, however, requires both a special hull design and development of an active flow control system. Such a system will stabilize the cavity under perturbations of incoming flow in seas. The paper includes an analysis of achievements in drag reduction, description of design fundamentals of ships with cavitating hulls/elements, and suggestions on application of ship drag reduction by cavitation.

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