The Effect of Flow Coefficient on the Self Noise Generated by a Ducted Rotor

2008 ◽  
Author(s):  
David B. Stephens ◽  
Scott C. Morris ◽  
William K. Blake
Keyword(s):  
Flow Field ◽  
The Self ◽  
Flow Coefficient ◽  
Hot Wire ◽  
Fluid Forces ◽  
Inflow Turbulence ◽  
Order Change ◽  
Ducted Rotor ◽  
Unsteady Fluid ◽  
Rigid Surfaces

Sound generation in low Mach number turbomachines is typically dominated by unsteady fluid forces on rigid surfaces. As a result, the radiated sound is closely related to the unsteady flow field. The present study focused on the self noise that is generated by a ducted rotor separate from the effect of noise due to inflow turbulence. The flow rate through the rotor was independently varied in order change the mean lift on the blades. Measurements of the flow field around a ducted rotor were found to provide insight to the various mechanisms of sound that are present at different mean loading conditions. At lower flow rates the blades were partially stalled, resulting in significantly increased noise levels. The measurements included rotor wake measurements using hot-wire anemometry and far field sound. A simple model to predict the radiated self noise based on the hot-wire measurements is presented.

The Control Method with Energy Saving of the Inflow Turbulence for Router Cooling Fan

2014 ◽  
Vol 886 ◽  
pp. 394-397 ◽  
Author(s):  
Ying Bo Xu ◽  
Xiao Dong Li
Keyword(s):  
Flow Field ◽  
Energy Saving ◽  
Turbulence Intensity ◽  
Control Method ◽  
Hot Wire ◽  
Mean Flow ◽  
Cooling Fan ◽  
Inflow Turbulence ◽  
The Mean

In this paper, the characteristics of the inflow turbulence intensity of a router cooling fan are studied experimentally. Screens with different parameters are designed to control the inflow turbulence intensity. The flow field is measured by hot-wire anemometer. The results show that the inflow turbulence intensity is closely connected with the parameters of the control screens. The inflow turbulence intensity can be significantly reduced when the screen with small meshes is used, while the mean flow is barely affected by the screen.

The Unsteady Fluid Flow Due to Corona Discharge in a System of Wire and Plate Electrodes

2002 ◽  
Author(s):  
Yusuke Imai ◽  
Yoshiaki Itoh ◽  
Hideyuki Mihira ◽  
Masatsugu Yoshizawa
Keyword(s):  
Flow Field ◽  
Corona Discharge ◽  
Point Of View ◽  
Laser Doppler Velocimeter ◽  
Physical Point ◽  
Fluid Force ◽  
Fluid Forces ◽  
Unsteady Fluid Flow ◽  
The Wire ◽  
Unsteady Fluid

Lateral oscillation of a wire electrode occurs when high dc voltage is applied between a wire and plate electrodes in an electrostatic field with corona discharge. The feature is that the horizontal component of the wire oscillation gradually increases and is excited with the fundamental natural frequency of the wire oscillation. We have already discussed the effects of the electrostatic and the fluid forces on the wire oscillation from the physical point of view. The fluid force on the wire due to corona wind was assumed to be one of main reasons for the outbreak mechanism of the wire oscillation. However, the outbreak mechanism of the wire oscillation has not been given yet. The main purpose of this paper is to examine another possible reason for the outbreak mechanism of the wire oscillation due to the fluid force. Some experiments are made to investigate whether oscillation of a non-conductive string, placed in the flow field, is excited by the fluid force or not. Moreover, the PIV (Particle Image Velocimetry) and the LDV (Laser Doppler Velocimeter) techniques are used to measure the flow field to confirm the hypothesis of the outbreak mechanism t hat the wire oscillation is excited due to the fluctuation of the fluid force on the wire.

Three-Dimensional Flow Field in Rocket Pump Inducers—Part 2: Three-Dimensional Viscid Flow Analysis, and Hot Wire Data on Three-Dimensional Mean Flow and Turbulence Inside the Rotor Passage

1977 ◽  
Vol 99 (1) ◽  
pp. 176-186 ◽  
Author(s):  
B. Lakshminarayana ◽  
C. A. Gorton
Keyword(s):  
Flow Field ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Flow Coefficient ◽  
Experimental Investigations ◽  
Complex Nature ◽  
Hot Wire ◽  
Mean Flow ◽  
Three Dimensional Flow ◽  
Dimensional Flow

This paper reports the measurement and prediction of the three-dimensional flow field in an axial flow inducer operating at a flow coefficient of 0.065 with air as the test medium. The experimental investigations included measurement of the blade static pressure and blade limiting streamline angle, and measurement of the three components of mean velocity, turbulence intensities and turbulence stresses at locations inside the inducer blade passage utilizing a rotating three-sensor hot-wire probe. Analytical investigations were conducted to predict the three-dimensional inviscid flow and to approximately predict the three-dimensional viscid flow by incorporating the dominant viscous terms into the exact equations of motion in rotating coordinate system. Radial velocities are found to be of the same order as axial velocities and total relative velocity distributions indicate a substantial velocity deficiency near the tip at mid-passage. High turbulence intensities and turbulence stresses are concentrated within this core region. Evidence of boundary layer interactions, blade blockage effects, radially inward flows, annulus wall effects and back-flows are all found to exist within the long, narrow passages of the inducer, emphasizing the complex nature of inducer flow which makes accurate prediction of the flow behavior extremely difficult.

Characteristics of Stable Rotating Stall Cells in an Axial Compressor

2017 ◽  
Author(s):  
Adam R. Hickman ◽  
Scott C. Morris
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Pressure Ratio ◽  
Pressure Sensors ◽  
Axial Compressor ◽  
Field Measurements ◽  
Rotating Stall ◽  
Flow Coefficient ◽  
Stable Operation ◽  
Double Phase

Flow field measurements of a high-speed axial compressor are presented during pre-stall and post-stall conditions. The paper provides an analysis of measurements from a circumferential array of unsteady shroud static pressure sensors during stall cell development. At low-speed, the stall cell approached a stable size in approximately two rotor revolutions. At higher speeds, the stall cell developed within a short amount of time after stall inception, but then fluctuated in circumferential extent as the compressor transiently approached a stable post-stall operating point. The size of the stall cell was found to be related to the annulus average flow coefficient. A discussion of Phase-Locked Average (PLA) statistics on flow field measurements during stable operation is also included. In conditions where rotating stall is present, flow field measurements can be Double Phase-Locked Averaged (DPLA) using a once-per-revolution (1/Rev) pulse and the period of the stall cell. The DPLA method provides greater detail and understanding into the structure of the stall cell. DPLA data indicated that a stalled compressor annulus can be considered to contained three main regions: over-pressurized passages, stalled passages, and recovering passages. Within the over-pressured region, rotor passages exhibited increased blade loading and pressure ratio compared to pre-stall values.

Effects of Stator Wakes and Spanwise Nonuniform Inlet Conditions on the Rotor Flow of an Axial Turbine Stage

1993 ◽  
Vol 115 (1) ◽  
pp. 128-136 ◽  
Author(s):  
J. Zeschky ◽  
H. E. Gallus
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Axial Flow ◽  
Tip Clearance ◽  
Hot Wire ◽  
Turbine Stage ◽  
Static Pressure Distribution ◽  
Inlet Conditions ◽  
Experimental Values ◽  
Rotor Flow

Detailed measurements have been performed in a subsonic, axial-flow turbine stage to investigate the structure of the secondary flow field and the loss generation. The data include the static pressure distribution on the rotor blade passage surfaces and radial-circumferential measurements of the rotor exit flow field using three-dimensional hot-wire and pneumatic probes. The flow field at the rotor outlet is derived from unsteady hot-wire measurements with high temporal and spatial resolution. The paper presents the formation of the tip clearance vortex and the passage vortices, which are strongly influenced by the spanwise nonuniform stator outlet flow. Taking the experimental values for the unsteady flow velocities and turbulence properties, the effect of the periodic stator wakes on the rotor flow is discussed.

Characteristics of Dynamic Forces Generated by a Flapping Butterfly and its Wake Structure

2017 ◽  
Author(s):  
Masaki Fuchiwaki ◽  
Kazuhiro Tanaka
Keyword(s):  
Flow Field ◽  
Butterfly Wing ◽  
Vortex Loop ◽  
Insect Wing ◽  
Fluid Forces ◽  
Insect Wings ◽  
Piv Measurement ◽  
Dynamic Forces ◽  
Butterfly Wings ◽  
The Relationship

A typical example of the flow field around a moving elastic body is that around butterfly wings. Butterflies fly by skillfully controlling this flow field, and vortices are generated around their bodies. The motion of their elastic wings produces dynamic fluid forces by manipulating the flow field. For this reason, there has been increased academic interest in the flow field and dynamic fluid forces produced by butterfly wings. A number of recent studies have qualitatively and quantitatively examined the flow field around insect wings. In some such previous studies, the vortex ring or vortex loop formed on the wing was visualized. However, the characteristics of dynamic forces generated by the flapping insect wing are not yet sufficiently understood. The purpose of the present study is to investigate the characteristics of dynamic lift and thrust produced by the flapping butterfly wing and the relationship between the dynamic lift and thrust and the flow field around the butterfly. We conducted the dynamic lift and thrust measurements of a fixed flapping butterfly, Idea leuconoe, using a six-axes sensor. Moreover, two-dimensional PIV measurement was conducted in the wake of the butterfly. The butterfly produced dynamic lift in downward flapping which became maximum at a flapping angle of approximately 0.0 deg. At the same time, the butterfly produced negative dynamic thrust during downward flapping. The negative dynamic thrust was not produced hydrodynamically by a flapping butterfly wing because a jet was not formed in front of the butterfly. The negative dynamic thrust was the kicking force for jumping and the maximum of this kicking force was about 6.0 times as large as the weight. On the other hand, the butterfly produced dynamic thrust in upward flapping which was approximately 6.0 times as large as the weight of the butterfly. However, the attacking force by the abdomen of the butterfly was included in the dynamic thrust and we have not yet clarified quantitatively the dynamic thrust produced by the butterfly wing.

scholarly journals Three-Dimensional Wake Decay Inside of a Compressor Cascade and its Influence on the Downstream Unsteady Flow Field: Part I — Wake Decay Characteristics in the Flow Passage

1990 ◽  
Author(s):  
C. Poensgen ◽  
H. E. Gallus
Keyword(s):  
Flow Field ◽  
Turbulent Flows ◽  
Velocity Vector ◽  
Three Dimensional ◽  
Time Dependent ◽  
Major Influence ◽  
Hot Wire ◽  
Compressor Cascade ◽  
Flow Passage ◽  
Turbulent Flow Field

A measuring technique based on multisensor hot-wire anemometry has been developed to determine the unsteady three-dimensional velocity vector and the structure of turbulent flows. It then has been applied to the passage and the exit flow of an annular compressor cascade, which is periodically disturbed by the wakes of a cylinder rotor, located about 50 percent of blade chord upstream. In part I of this paper the decay of the rotor wakes will be described first without stator and secondly through a stator passage. The time-dependent turbulent flow field downstream of this stator is discussed in Part II. The rotor wakes have a major influence on the development of three-dimensional separated regions inside the compressor cascade, and this interaction will be addressed in both parts of this paper.

scholarly journals Investigation of the velocity field downstream of a benchmark vent using numerical simulation and hot-wire anemometry

2019 ◽  
Vol 213 ◽  
pp. 02076
Author(s):  
Jan Sip ◽  
Frantisek Lizal ◽  
Jakub Elcner ◽  
Jan Pokorny ◽  
Miroslav Jicha
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Velocity Field ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Turbulence Models ◽  
Hot Wire ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Precise Prediction

The velocity field in the area behind the automotive vent was measured by hot-wire anenemometry in detail and intensity of turbulence was calculated. Numerical simulation of the same flow field was performed using Computational fluid dynamics in commecial software STAR-CCM+. Several turbulence models were tested and compared with Large Eddy Simulation. The influence of turbulence model on the results of air flow from the vent was investigated. The comparison of simulations and experimental results showed that most precise prediction of flow field was provided by Spalart-Allmaras model. Large eddy simulation did not provide results in quality that would compensate for the increased computing cost.

Sign in / Sign up

Export Citation Format

Share Document