Yaw Meter Research Articles

Experimental Study on Flow Field Characteristics of a Free Circular Swirling Jet

Flow field characteristics of a free circular swirling jet are investigated in the present study considering three different swirl numbers 0.38, 0.56 and 0.80. The experiment is carried out in an air jet facility for Reynolds numbers 16300, 34400 and 49200. Pressure probe method is used for 3-hole wedge shaped yaw meter to measure and calculate the data. Mean flow velocity along with centerline mean velocity decay are analyzed where swirl changes the instinctive properties of circular jet and demolishes the potential core. Swirl motion creates negative flow field which changes the static pressure and kinetic energy distribution enormously. As a result, flow diverges earlier, and surrounding air enters into the flow field more rapidly which enhances the mixing performance of the jet.

Experimental Study on Flow Field Characteristics of a Free Circular Swirling Jet

Flow field characteristics of a free circular swirling jet are investigated in the present study considering three different swirl numbers 0.38, 0.56 and 0.80. The experiment is carried out in an air jet facility for Reynolds numbers 16300, 34400 and 49200. Pressure probe method is used for 3-hole wedge shaped yaw meter to measure and calculate the data. Mean flow velocity along with centerline mean velocity decay are analyzed where swirl changes the instinctive properties of circular jet and demolishes the potential core. Swirl motion creates negative flow field which changes the static pressure and kinetic energy distribution enormously. As a result, flow diverges earlier, and surrounding air enters into the flow field more rapidly which enhances the mixing performance of the jet.

Experimental Study of Twin Connected Pipe Jets

Two parallel pipe jets of 20 mm diameter were placed 1.2 mm diameter apart and were connected by a 4 mm wide channel all along the central plane of the jets. The mean velocity flow field of the jets was investigated for three Reynolds number 16300, 34400 and 49200. The Reynolds number was based on the exit velocity of the jets and jet diameter. The experiment was performed in an air jet facility and yaw meter was used for measurement of mean velocity and its direction. Their variations along the longitudinal, transverse, and lateral directions have been analyzed. A significant change of the jet flow field is observed near the exit of the jet. The combined effect of the jets diminishes the presence of recirculation region at the immediate exit rather enhances the energy and momentum transfer between their individual flow fields. Static pressure and kinetic energy distribution are also studied and a momentous variations have been noticed with varying Reynolds number.

Experimental Study of Twin Connected Pipe Jets

Two parallel pipe jets of 20 mm diameter were placed 1.2 mm diameter apart and were connected by a 4 mm wide channel all along the central plane of the jets. The mean velocity flow field of the jets was investigated for three Reynolds number 16300, 34400 and 49200. The Reynolds number was based on the exit velocity of the jets and jet diameter. The experiment was performed in an air jet facility and yaw meter was used for measurement of mean velocity and its direction. Their variations along the longitudinal, transverse, and lateral directions have been analyzed. A significant change of the jet flow field is observed near the exit of the jet. The combined effect of the jets diminishes the presence of recirculation region at the immediate exit rather enhances the energy and momentum transfer between their individual flow fields. Static pressure and kinetic energy distribution are also studied and a momentous variations have been noticed with varying Reynolds number.

Operation in the turbulent jet field of a linear array of multiple rectangular jets using a two-dimensional jet (Variation of mean velocity field)

The mean flowfield of a linear array of multiple rectangular jets run through transversely with a two-dimensional jet, has been investigated, experimentally. The object of this experiment is to operate both the velocity scale and the length scale of the multiple rectangular jets using a two-dimensional jet. The reason of the adoption of this nozzle exit shape was caused by the reports of authors in which the cruciform nozzle promoted the inward secondary flows strongly on both the two jet axes. Aspect ratio of the rectangular nozzle used in this experiment was 12.5. Reynolds number based on the nozzle width d and the exit mean velocity Ue (≅ 39 m / s) was kept constant 25000. Longitudinal mean velocity was measured using an X-array Hot-Wire Probe (lh = 3.1 μm in diameter, dh = 0.6 mm effective length : dh / lh = 194) operated by the linearized constant temperature anemometers (DANTEC), and the spanwise and the lateral mean velocities were measured using a yaw meter. The signals from the anemometers were passed through the low-pass filters and sampled using A.D. converter. The processing of the signals was made by a personal computer. Acquisition time of the signals was usually 60 seconds. From this experiment, it was revealed that the magnitude of the inward secondary flows on both the y and z axes in the upstream region of the present jet was promoted by a two-dimensional jet which run through transversely perpendicular to the multiple rectangular jets, therefore the potential core length on the x axis of the present jet extended 2.3 times longer than that of the multiple rectangular jets, and the half-velocity width on the rectangular jet axis of the present jet was suppressed 41% shorter compared with that of the multiple rectangular jets.

Performance Evaluation of Yaw Meter with the Aid of Computational Fluid Dynamic

A multi-hole conical probe is employed to determine the velocity of the air flow, total and static pressures of the wind tunnel, wave angle in addition to estimating the noise of the test segment. It twinkles with the unique qualities of being trouble-free, vigorous with the flexibility to be applied even in ruthless situations. Our innovative conical wedge type probe is launched by means of AUTOCAD and engineered by exploiting the stain less steel material. The pressure holes are situated at the end of the conical probe which is applied to calculate the pressure and flow velocity of the atmosphere. The novel probe is performed at supersonic settings by the effective use of the proficient Computational Fluid Dynamic Analysis (CFD analysis) software. It discharges the task of assessing the enduring competence of the projected probe under a variety of situations like fixed pressure and temperature along with the velocity of the air flow at different mach-numbers. This sample fashioned blueprint built up in CFD is estimated under supersonic backdrops up to mach 3. Thus, it is crystal clear that that our well-conceived sample developed with semi nose angle 20o ushers in a sterling performance in mach 2.8 triggering an incredible shock wave of 29.3o

複数長方形噴流場の二次元噴流による操作（平均速度場の変化）

The mean flowfield of a linear array of multiple rectangular jets run through transversely with a normal two-dimensional jet, has been investigated, experimentally. The purpose of this experiment is to operate both the velocity scale and the length scale of the multiple rectangular jets using a two-dimensional jet. The reason of the adoption of this nozzle exit shape was caused by the reports of authors in which the cruciform nozzle jet promoted strongly the inward secondary flows on both the two jet axes. Aspect ratio of the rectangular nozzle used in this experiment was 12.5. Reynolds number based on the nozzle width d and the exit mean velocity Ue (≡39m/s) was kept constant 25000. Longitudinal mean velocity was measured using an X-array Hot-Wire Probe (3.1 μm in diameter, 0.6 mm effective length) operated by the linearized constant temperature anemometers (DANTEC), and the spanwise and the lateral mean velocities were measured using a yaw meter. The signals from the anemometers were passed through the low-pass filters and sampled using A.D. converter. The processing of the signals was made by a personal computer. Acquisition time of the signals was usually 60 seconds. From this experiment, it was revealed that the inward secondary flows on both the y and z axes in the upstream region were promoted by a two-dimensional jet which run through transversely to the multiple rectangular jets, therefore the potential core length on the x axis of the present jet became 2.5 times longer than that of the supposed multiple rectangular jets, and the half-velocity width on the multiple rectangular jet axes of the present jet was suppressed 50% shorter compared with that of the supposed multiple rectangular jets.

Turbulent jets issuing from rectangular nozzle with a rectangular notch at the midspan

The turbulent flowfield of turbulent jet issuing from rectangular nozzle (Aspect Ratio=12.5) with a rectangular notch at the midspan, has been investigated experimentally. Four aspect ratios of rectangular notch (NAR: Notch Aspect Ratio) used in this experiment were 2.5, 7.5, 12.5 and 165. The Reynolds number based on the nozzle width d and the exit mean velocity Ue, was kept constant 30000 (NAR=2.5 and 7.5), 15000 (NAR=12.5) and 13000 (NAR=165), respectively. Longitudinal mean velocity and turbulent intensities were measured using an X-array Hot-Wire Probe (5 µm in diameter, 1 mm effective length) operated by the linearized constant temperature anemometers (DANTEC), and the spanwise and the lateral mean velocities were measured using a yaw meter. The signals from the anemometers were passed through the low-pass filters and sampled using A.D. converter. The processing of the signals was made by a personal computer. Acquisition time of the signals was usually 80 seconds. From this experiment, it was revealed that the attachment of a rectangular notch to the rectangular jet suppressed the development of the turbulent velocity scales near the jet centre in the upstream region for the cases of NAR≥7.5.

Experimental observations of the merger of co-rotating wake vortices

The interaction and merger of a pair of co-rotating vortices has been studied experimentally in a wind tunnel. The vortices are generated using two separate wings, allowing both initial circulation ratio and initial separation to be varied. At the nominal test speed of 30 ms−1, the circulation-based Reynolds number is typically 6.4 × 104. Mean crossflow velocities at stations downstream are obtained with a traverse-mounted yaw meter. The vortex interaction is characterized by fitting Lamb–Oseen profiles to the measured, azimuthally averaged, tangential velocity profiles.It is found that the merger process differs in several important respects from lower-Reynolds-number studies. First, the separation of the vortices decreases continually throughout the initial, ‘viscous growth’, phase, instead of remaining constant. Second, the vortex core growth in this phase appears to be greater than can be accounted for by turbulent diffusivity, even after correcting for the effects of wandering. Finally, the time to merger lies well below that predicted by expressions based on the lower-Reynolds-number observations, and is further reduced when the circulation ratio departs from unity. We conclude that the enhanced core growth is probably due to the short-wavelength ‘elliptic’ instability that has already been observed in some high-Reynolds-number experiments. The mechanism behind the decrease in separation, which is a crucial factor in the reduced merger time, is three-dimensional, but, beyond this, remains unknown.

Testing Block Probes for Wall Shear Stress Measurement in Water Flows

The authors developed and tested two types of sublayer pressure probe or blocks, to indirectly measure the average modulus and direction of the wall parallel component of the shear stress tensor, usually referred to as wall shear stress, or boundary shear, in water flows. The local shear stress has been investigated by means of a Preston tube for different Reynolds numbers, in a smooth rectangular section duct. The observed data have been used to calibrate the blocks. The blocks’ design is a direct outcome of the Dexter yaw meter, developed to function in an air flow. The observed pressure field associated with a given shear stress is compared to its theoretical counterpart, based on the assumption that the velocity profile satisfies a two-dimensional law of the wall, for smooth boundary.

Modelling, calibration, and error analysis of seven-hole pressure probes

This report describes the calibration of a non-nulling, conical, seven-hole pressure probe over a large range of flow onset angles. The calibration procedure is based on the use of differential pressures to determine the three components of velocity. The method allows determination of the flow angle and velocity magnitude to within an average error of 1.0° and 1.0% respectively. Greater accuracy can be achieved by using high quality pressure transducers. Also included is an examination of the factors which limit the use of the probe, a description of the measurement chain, an error analysis, and a typical experimental result. In addition, a new general analytical model of pressure probe behavior is described and the validity of the model is demonstrated by comparing it with experimentally measured calibration data for a three-hole yaw meter and a sevenhole probe.

Photographic surveying of flow speed and direction adjacent to a surface

SummaryA flow surveying technique is described which provides a direct and quick output of either flow speed or direction. The computer based system enables ‘contour plots’ of these quantities to be obtained for fixed offset distances from a surface, using a series of surface contacting cylindrical probes. Pre-set values of the signal from the flow sensing system are used to switch a tri-coloured light source which traverses in unison with the probe, while a time exposure photograph is taken. For flow direction measurement, the signal activating the lights is computed from the pressure difference between yaw meter tappings on the cylinder in conjunction with the cylinder base pressure. Flow velocity is obtained from the base pressure alone, or alternatively from a hot wire probe.Results are presented to show that the method can provide useful and detailed data. It is seen mainly as a complement to other methods available for visualising complex flows.

Effect of turbulence on pressure probes

The mean pressure coefficients indicated by several types of static pressure probe and yaw meter have been measured in turbulent flow on the center line of a circular jet where the normal-component RMS turbulent intensity is about 0.24 of the mean velocity, for a range of yaw angles and a range of ratios of tube size to typical eddy size. For mean yaw angles greater than about 10 degrees , yaw meter calibrations differ significantly between turbulent and non-turbulent flow: this is because of the nonlinearity of the calibration at higher yaw angles, which are reached instantaneously. The response of a disc static tube, whose yaw calibration becomes nonlinear at quite small angles, is spectacularly altered by turbulence in the stream, and the use of this device in turbulent flow cannot be recommended.

Effect of Hydrostatic Pressure on Underwater Towed Body Cable Confuguration

response curve since with a nonlinear curve the value given will be neither an average nor the value at a particular yaw angle. It would therefore be advantageous to redefine the yaw meter sensitivity C^ which would be appropriate when the yaw meter is kept stationary and the flow angle is evaluated by using a calibration curve. In this case it would be useful to know the average sensitivity over the range of yaw angles being considered, viz.

Definition of a Yaw Meter Sensitivity for the "Null Reading" Technique

Definition of a Yaw Meter Sensitivity for the "Null Reading" Technique

A Pitch and Yaw Meter

A Pitch and Yaw Meter

A Study of the Flow Patterns in an Impeller Channel of a Radial Turbine : In the Case of a Radial Blade Impeller

Results of some experimental investigations of flow in rotating impeller passages of a radial turbine are presented. Velocity and static pressure measurements were made with a yaw meter probe fitted within the impeller channel of the rotating impeller. The influences of two performance parameters, i.e. non-dimensional weight flow and non-dimensional rotation speed on the flow behavior within the impeller passage are shown. Further, the flow patterns in blade-to-blade planes are shown for three different passage depthes. In addition, a theoretical analysis for mixed flow type is made, which includes the inward-flow type as a special case. For the necessary boundary values at inlet of the impeller in the theoritical study, we use the values observed in the experiment. Theoretical results show a fairly good agreement with the experimental data.

An Investigation of Element Performance of Rotating Blade of a Single-Stage Axial-Flow Blower

A blade of rotor with the type NACA-64 was tested with a low-speed test blower. Certain special techniques were applied to the measurements of the blow condition, namely, the measurements of pressure distribution on rotating blades and the measurement using a yaw meter which rotates with the rotor, etc. The measured blade-element performance was compared with the performace estimated from cascade data over a broad range of the incidence angles. As a result of this investigation, the turning and deviation angles of the rotor were found to agree with cascade data in the region of the annulus free from wall boundary-layer effects. The wake from upstream of the rotor causes the separation of the flow on the blade surface at a flow rate larger than the undisturbed flow. When the wake goes out through the rotor, the low-energy air of the wake experiences a greater turning than that of the main stream.

A Study on Flow in Centrifugal Impellers with Passages of Circular-Arc in Meridional Plane

The flow in the impeller is affected by the incidence angle. The impellers used in this experiments are of three types ; two of which have constant passage height, but one is with an inducer and another is without, and the other has a constant sectional area all on the way from inlet to outlet, but without any inducer. The influence of incidence angle to the flow in impeller has been measured by the kiel probe and the yaw meter that rotate with the impeller. From this results, it has been recognized that the separation of the flow occurs at the triangle-area that is surrounded by the trailing face of blade and the shroud. The pressure distribution at blade face that has been measured in the experiments is compared with the results of the two-dimensional theory. This theory is found to be in comparatively good agreement with the experimental results, that is, the pressure at the blade face is influenced by the main flow only, and it hardly affected by the secondary flows that complicate the flow through the impeller.

Experimental Study on Radial Turbine, with Special Reference to the Influence of the Number of Impeller Blades on Performance Characteristics

Experiments were conducted to ascertain the influence of the number of impeller blades on the performance characteristics of a radial turbine. Thus, impellers fitted with 4, 8, 16, 24 and 32 blades respectively were employed, and the radial turbine was driven by compressed air delivered from Roots blowers. Besides usual measurements of pressures and temperatures, the flow directions as well as the magnitudes of the absolute velocities at the entrance of the impeller were made by a yaw meter. The following results were obtained. (1) The optimum number of impeller blades of a radial turbine is not less than that of a centrifugal compressor. (2) In regions of maximum overall adiabatic efficiencies, the relative velocities at the entrance of the impeller decline rotationwise by the angles 20∼30 degrees.