Static Pressure Holes Research Articles

Active Stall Control System on NACA0012 by Using Synthetic Jet Actuator

Flow separation is typically an undesirable phenomenon, and boundary layer control is an important technique for the separation problems on airfoils. The synthetic jet actuator is considered as a promising candidate for flow control applications because of its compact nature and ability to generate momentum without the need for fluidic plumbing. In the present study, an active separation control system using synthetic jets is proposed and practically applied to the stall control of the NACA0012 airfoil in a wind tunnel test. In our proposed system, the flow conditions (stalled or unstalled) can be judged by calculating from two static pressure holes on the airfoil upper surface alone. The experimental results indicate that the maximum lift coefficient increases by 11% and the stall angle rises by 4° in contrast to the case under no control. It is confirmed that our proposed system can suppress the stall on the NACA0012 airfoil and that the aerodynamic performance of the airfoil can be enhanced. The proposed system can also be operated prior to the onset of stall. Therefore, separation control is always attained with no stall for all flow fields produced by changing the angle of attack that were examined.

Characteristic evaluation of stemless Pitot static tubes aimed to optimize the position of static pressure holes

Characteristic evaluation of stemless Pitot static tubes aimed to optimize the position of static pressure holes

Model of Forming-Accretion on Blast Furnace Copper Stave and Industrial Application

Copper staves have been equipped on nearly all of BF (blast furnaces) with volume over than 1000 m3 in China since their introduction from abroad about more than 10 years ago. Because of short application and lack of experience, phenomena of thickened or naked of copper stave happen occasionally which influence production severely. So it is important to study the model of forming-accretion on BF copper stave and realize real-time monitoring of forming-accretion on different copper staves. Therefore, mathematic model of calculating accretion thickness by heat flow of BF is proposed, and the calculated results indicate that accretion thickness could be kept at a reasonable range of around 50 mm by controlling heat flux around 22.0 kW/m2. The monitoring program based on the model was applied to a certain BF in China successfully, and it is found that slip of BF near the inner wall is one of most important reasons that cause fluctuation of accretion thickness. During the period of scheduled maintenance of the certain BF, the thickness of accretion measured through the static pressure holes is in good accordance with the value calculated by the monitoring program, so the results calculated by the monitoring program can be used to guide industrial production.

Prediction and Measurement of Pressure Distribution Over a Compressor Blade Through A Cascade Studies

The base of this paper is to find the pressure distribution over the compressor blades through a cascade, which is useful to measure the flow properties of the compressor in an actual axial compressor. The static pressure distribution is obtained from the static pressure holes around the central blade which equipped with the manometers. Plot the graph between the pressure distribution and the spacing between the leading edge to the static holes. And we have to predict the Mach number doing the same procedure to get the results. After that experimental result, we have to analyze the whole experimental cascade series of blade by using software. A result from the software is compared with the experimental measurements. We have to predict the Mach number and change the pitch of the blades and the blade angle do the same procedure as mentioned before and take different plots to analyze in which parameters the compressor blades are got the optimum pressure rise.

Wind tunnel CESAR model

Wind tunnel CESAR model

Experimental investigation of flow characteristics of a magnetohydrodynamic (MHD) duct of fan-shaped cross section

Experiments along with numerical calculations are carried out to investigate the effect of the geometry of the cross section on flow characteristics of a MHD propulsion duct. A fan-shaped cross-section MHD thruster duct is chosen for comparison with a previously investigated rectangular cross section. Measurement of the velocity field is made using LDV (Laser Doppler Velocimetry) system with a fiber-optic cable and pressure distribution is measured with static pressure holes at the bottom surface. Comparison with rectangular cross section shows that the velocity profile is significantly influenced by the geometry of cross section while the axial pressure distribution is not so affected.

A Method for Correcting Wall Pressure Measurements in Subsonic Compressible Flow

A theoretical and experimental investigation has been made of the static pressure hole problem in subsonic flow. Thanks to a linearization, the effects of the boundary layer, of the velocity gradient and of the wall curvature could be separated so that a formula of correction containing three influence functions has been obtained. These functions were determined in the case of practical requirements by means of experiments made on appropriate models for two values of the depth-to-diameter ratio and for at least three values of the Mach number. Then, the method of correction has been applied to the flow around an airfoil at zero angle of attack.

Influence of drag reducing polymers on the turbulent boundary layer of a body of revolution

In the application of polymers for the drag reduction of ships, the study of outer boundary layer flows is a pre-requisite. The static pressures and the velocity profiles in the boundary layer of a body of revolution at 24 static pressure holes and six Pitot tube rakes with five tubes each are measured by means of differential pressure transducers in connection with electronic data acquisition and processing. A comparison is made between water and homogeneous solutions of Polyox Coagulant in eight concentrations from 0.5 to 100 ppmw at Reynolds numbers from 106 to 8×106. Comparing the static pressure coefficients, a shift to higher values is observed especially behind the front pressure minimum with increasing polymer concentrations. The calculated specific pressure resistance coefficients CPV show smaller values with higher concentrations indicating the influence of drag reducing polymers on boundary layer development. From the velocity profiles measured with the Pitot tube rakes the boundary layer thicknesses are calculated. They become smaller with higher polymer concentrations up to a limiting concentration and then they grow sharply by some hundred percent. The limiting value increases with flow velocity. Some of these effects may depend on the measuring method, i.e., Pitot tube errors in drag reducing liquids, degradation, and the turbulence in the circulating water tank, although these influences were checked. Therefore, interpretation of the measured values may not be quite conclusive.

Absolute measurements of static-hole error using flush transducers

Experiments are reported in which the error of a sharp-edged, circular static pressure hole normal to the boundary of a moving fluid is deduced from measurements made with pressure transducers, the diaphragms of which were set flush with the boundary surface. An error curve is presented which covers the range of hole Reynolds number up to a value of 2000.

Simplification of the Razor Blade Technique and its Application to the Measurement of Wall-Shear Stress in Wall-Jet Flows

SummaryExperiments in a in (6-35 mm) channel have yielded further information on the precision and convenience of the razor blade technique. It is shown that adhesive tape or carefully located cement can be used to secure a segment of razor blade over a static pressure hole: the resulting calibration for shear stress remains valid if the blade is removed and relocated over the same or a different, similar sized hole. Razor blade segments, calibrated in this manner, have been used to measure wall-shear stress in a turbulent boundary layer with tangential, secondary injection: the results indicate that V. C. Patel’s law of the wall is valid for such flows.

Utilisation des cannes dérivées du tube de pitot pour l'étude des débits dans les conduites

1. The author states the problem as having to determine a simple instrument capable of being introduced without difficulty and at little cost at any point in the pipes constituting the Paris Prefecture's water distribution loop system. His choice fell on a cylindrical tube derived from the Pitot tube, featuring two dynamic pressure tappings and no static pressure hole in order to increase the differential pressure. 2. On calibrating this probe in an infinite medium in the French Navy's hull testing tank, it was found that the conventional formula Q = K D2 Ha relating discharge to average velocity Vm gave two values of the exponent a, both of which were dose to 1/2, and that the discontinuity invariably occurred at a velocity in the neighbourhood of 1 m/sec. 3. The author decided to always measure the velocity in the centre Vo in order to reduce the margin of uncertainty to a minimum. He made measurements on a large number of pipes with widely varying velocity distribution curves in order to determine the maximum probable variation range of coefficient v = mean velocity/central velocity 4. The author was then able to plot a graph consisting of a family of straight lines on a double logarithmic scale, the spacing of which was related to pipe diameter by a parabolic law. 5. The author then goes on to show successive applications of the probe in the Paris Prefecture's water distribution system, including one probe permanently installed in a 1.5 m diameter pipe. 6. Finally, the author argues in favour of the use of these probes for investigation and supervisory purposes and not as precision instruments-as a means of establishing basic requirements for operation ensuring optimum running economy, combined with satisfactory service to the consumer.

The Static Hole Pair as a Skin Friction Meter

In a recent technical note Rajaratnam has pointed out the possibility of using the pressure difference measured between two static pressure holes of different diameter as a means of determining skin friction. The device exploits the fact that for any hole there is an error in measurement of static pressure which depends both on the hole diameter and on local skin friction, as Shaw has demonstrated. Consequently the difference in pressure measured between two adjacent holes of different diameter will be a function of the skin friction. In this note the device will be called a “static hole pair”. The larger hole will be referred to as the “test” hole, and the smaller hole as the “reference” hole.

CALIBRATION OF THE ALNOR DUCT JET (DOUBLE PITOT TUBE) WITH SECTIONED EXTENSIONS FOR STACK SAMPLING.

Abstract Fly-ash loading of stack gas frequently precludes velocity measurements with a standard Pitot tube due to plugging of the static pressure holes. The use of a double Pitot tube obviates this difficulty, but in the lengths commercially available its use is restricted to stacks of about 30 inches in diameter. Calibration charts are presented demonstrating that an 18-inch double Pitot tube may be fitted with metal tubing extensions as necessary to allow velocity traverses of large stacks with only small departures from velocity meter scale readings.

The influence of hole dimensions on static pressure measurements

The pressure measured at a static pressure hole differs slightly from the true static pressure, by an amount which depends on the hole size and shape. The present investigation extends the range of previous work to determine the error in static pressure measurement in incompressible turbulent flow. The observed static pressure was always greater than the true static pressure. The results are presented in dimesionless form as a function of the Reynolds number based on hole diameter and friction velocity.