HPC-LES for Unsteady Aerodynamics of a Heavy Duty Truck in Wind Gust - 1st report: Validation and Unsteady Flow Structures

2010 ◽  
Author(s):  
Makoto Tsubokura ◽  
Kaito Takahashi ◽  
Tomofuyu Matsuuki ◽  
Takuji Nakashima ◽  
Takeshi Ikenaga ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Unsteady Aerodynamics ◽  
Flow Structures ◽  
Wind Gust ◽  
Heavy Duty ◽  
Heavy Duty Truck

Large Eddy Simulation on the Unsteady Aerodynamics of a Heavy Duty Truck in Wind Gust

2011 ◽  
Author(s):  
Makoto Tsubokura ◽  
Prasanjit Das ◽  
Tomofuyu Matsuuki ◽  
Takuji Nakashima
Keyword(s):  
Large Eddy Simulation ◽  
Numerical Method ◽  
Unsteady Aerodynamics ◽  
Static Condition ◽  
Wind Tunnels ◽  
Wind Gust ◽  
Heavy Duty ◽  
Heavy Duty Truck ◽  
Eddy Simulation ◽  
Large Eddy

Unsteady aerodynamic forces acting on a full-scale heavy duty truck were investigated using a large-eddy simulation technique. The numerical method adopted was first validated on a static condition measured at the DNW German-Dutch wind tunnels. After the correction of the blockage ratio in the wind tunnel, the drag coefficient obtained by our numerical method showed good agreement with the experimental data within the errors of less than 5%. Effect of an air deflector mounted on the top of a cabin was also discussed. Then the method was applied to non-stationary conditions in which the truck was subjected to ambient perturbation of approaching flow. The perturbation of the flow is a model of atmospheric turbulence and sinusoidal crosswind velocity profiles were imposed on the uniform incoming flow with its wavelength comparable to the vehicle length. As a result, it was confirmed that when the wavelength of the crosswind is close to the vehicle length, averaged drag increases by more than 10% and down-force decreases by about 60%, compared with the case without perturbation.

Coupled Analysis of Unsteady Aerodynamics and Vehicle Motion of a Heavy Duty Truck in Wind Gusts

2010 ◽  
Author(s):  
Takuji Nakashima ◽  
Makoto Tsubokura ◽  
Takeshi Ikenaga ◽  
Kozo Kitoh ◽  
Yasuaki Doi
Keyword(s):  
Vehicle Dynamics ◽  
Unsteady Aerodynamics ◽  
Dynamics Simulation ◽  
Coupled Analysis ◽  
Wind Gust ◽  
Strong Wind ◽  
Heavy Duty ◽  
Aerodynamic Forces ◽  
Heavy Duty Truck ◽  
Unsteady Aerodynamic

In the present study, unsteady aerodynamic forces acting on a simplified heavy duty truck in strong wind gust and their effects on the truck’s motion were investigated by using a coupled analysis. Unsteady fluid dynamics simulation was applied to numerically reproduce unsteady aerodynamic forces acting on the truck under sudden crosswind condition. Taking account of vehicle’s motion, moving boundary techniques were introduced. Motions of the truck were simulated by a vehicle dynamics simulation including a driver’s reaction. The equations of motion of the truck in longitudinal, lateral, and yaw-rotational directions were numerically solved. These aerodynamics and vehicle dynamics simulations were coupled by exchanging the aerodynamic forces and the vehicle’s motion. In order to investigate effects of the unsteady vehicle aerodynamics on the vehicle’s motion, conventional analysis of the vehicle’s motion using quasi-steady aerodynamic forces and one-way coupled analysis with fixed vehicle attitude were also conducted. The numerical results of these simulations were compared with each other, and the effects of the two kinds of unsteady aerodynamics were discussed separately and totally. In the sudden crosswind condition, the unsteady aerodynamics effected significantly on the truck’s motion. An effect of transient aerodynamics as the truck ran into a sudden crosswind was greater than an effect of unsteady aerodynamics caused by unsteady vehicle’s motion, while both of the effects showed significance.

scholarly journals Flow pattern similarities in the near wake of three bird species suggest a common role for unsteady aerodynamic effects in lift generation

2017 ◽  
Vol 7 (1) ◽  
pp. 20160090 ◽  
Author(s):  
Roi Gurka ◽  
Krishnamoorthy Krishnan ◽  
Hadar Ben-Gida ◽  
Adam J. Kirchhefer ◽  
Gregory A. Kopp ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Bird Species ◽  
Unsteady Aerodynamics ◽  
Flow Patterns ◽  
Flapping Flight ◽  
Wake Flow ◽  
Flapping Wings ◽  
Flow Structures ◽  
Near Wake ◽  
Time Resolved

Analysis of the aerodynamics of flapping wings has yielded a general understanding of how birds generate lift and thrust during flight. However, the role of unsteady aerodynamics in avian flight due to the flapping motion still holds open questions in respect to performance and efficiency. We studied the flight of three distinctive bird species: western sandpiper ( Calidris mauri ), European starling ( Sturnus vulgaris ) and American robin ( Turdus migratorius ) using long-duration, time-resolved particle image velocimetry, to better characterize and advance our understanding of how birds use unsteady flow features to enhance their aerodynamic performances during flapping flight. We show that during transitions between downstroke and upstroke phases of the wing cycle, the near wake-flow structures vary and generate unique sets of vortices. These structures appear as quadruple layers of concentrated vorticity aligned at an angle with respect to the horizon (named ‘double branch’). They occur where the circulation gradient changes sign, which implies that the forces exerted by the flapping wings of birds are modified during the transition phases. The flow patterns are similar in (non-dimensional) size and magnitude for the different birds suggesting that there are common mechanisms operating during flapping flight across species. These flow patterns occur at the same phase where drag reduction of about 5% per cycle and lift enhancement were observed in our prior studies. We propose that these flow structures should be considered in wake flow models that seek to account for the contribution of unsteady flow to lift and drag.

Dynamic effects on high frequency unsteady flow structures

1990 ◽  
Author(s):  
JOHN KLINGE ◽  
SCOTT SCHRECK ◽  
MARVIN LUTTGES
Keyword(s):  
Unsteady Flow ◽  
High Frequency ◽  
Flow Structures ◽  
Dynamic Effects

Helical Flow Disturbances in a Multi-Nozzle Combustor

2014 ◽  
Author(s):  
Michael Aguilar ◽  
Michael Malanoski ◽  
Gautham Adhitya ◽  
Benjamin Emerson ◽  
Vishal Acharya ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Field Measurements ◽  
Flow Fields ◽  
Helical Flow ◽  
Forced Response ◽  
Flow Structures ◽  
Response Dynamics ◽  
Flow Disturbances ◽  
Nozzle Configuration ◽  
Jet Interactions

This paper describes an experimental investigation of a transversely forced, swirl stabilized combustor. Its objective is to compare the unsteady flow structures in single and triple nozzle combustors and determine how well a single nozzle configuration emulates the characteristics of a multi-nozzle one. The experiment consists of a series of velocity field measurements captured on planes normal to the jet axis. As expected, there are differences between the single and triple-nozzle flow fields, but the differences are not large in the regions upstream of the jet merging zone. Direct comparisons of the time averaged flow fields reveal a higher degree of non-axisymmetry for the flowfields of nozzles in a multi-nozzle configuration. Azimuthal decompositions of the velocity fields show that the transverse acoustic forcing has an important influence on the dynamics, but that the single and multi-nozzle configurations have similar forced response dynamics near the dump plane. Specifically, the axial dependence of the amplitude in the highest energy axisymmetric and helical flow structures is quite similar in the two configurations. This result suggests that the hydrodynamic influence of one swirling jet on the other is minimal and, as such, that jet-jet interactions in this configuration do not have a significant influence on the unsteady flow structures.

Event-triggered control for hybrid power supply of fuel-cell heavy-duty truck

2021 ◽  
Vol 41 ◽  
pp. 102985
Author(s):  
Beichen Ding ◽  
Benfei Wang ◽  
Ronghui Zhang
Keyword(s):  
Fuel Cell ◽  
Power Supply ◽  
Heavy Duty ◽  
Hybrid Power ◽  
Heavy Duty Truck ◽  
Event Triggered
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