Tunnel Calibration Research Articles

Synthetic Wind Estimation for Small Fixed-Wing Drones

Wind estimation is crucial for studying the atmospheric boundary layer. Traditional methods such as weather balloons offer limited in situ capabilities; besides an Air Data System (ADS) combined with inertial measurements and satellite positioning is required to estimate the wind on fixed-wing drones. As pressure probes are an important constituent of an ADS, they are susceptible to malfunctioning or failure due to blockages, thus affecting the capability of wind sensing and possibly the safety of the drone. This paper presents a novel approach, using low-fidelity aerodynamic models of drones to estimate wind synthetically. In our work, the aerodynamic model parameters are derived from post-processed flight data, in contrast to existing approaches that use expensive wind tunnel calibration for identifying the same. In sum, our method integrates aerodynamic force and moment models into a Vehicle Dynamic Model (VDM)-based navigation filter to yield a synthetic wind estimate without relying on an airspeed sensor. We validate our approach using two geometrically distinct drones, each characterized by a unique aerodynamic model and different quality of inertial sensors, altogether tested across several flights. Experimental results demonstrate that the proposed cross-platform method provides a synthetic wind velocity estimate, thus offering a practical backup to traditional techniques.

High-resolution wind speed measurements with quadcopter uncrewed aerial systems: calibration and verification in a wind tunnel with an active grid

Abstract. As a contribution to closing observational gaps in the atmospheric boundary layer (ABL), the Simultaneous Wind measurement with Uncrewed Flight Systems in 3D (SWUF-3D) fleet of uncrewed aerial systems (UASs) is utilized for in situ measurements of turbulence. To date, the coefficients for the transformation terms used in our algorithm for deriving wind speeds from avionic data have only been determined via calibration flights in the free field. Therefore, we present in this work calibration and verification under laboratory conditions. The UAS measurements are performed in a wind tunnel equipped with an active grid and constant temperature anemometers (CTAs) as a reference. Calibration is performed in x- and y-coordinate directions of the UAS body frame at wind speeds of 2 … 18 m s−1. For systematic verification of the measurement capabilities and identification of limitations, different measurement scenarios like gusts, velocity steps, and turbulence are generated with the active grid. Furthermore, the measurement accuracy under different angles of sideslip (AoSs) and wind speeds is investigated, and we examined whether the calibration coefficients can be ported to other UASs in the fleet. Our analyses show that the uncertainty in measuring the wind speed depends on the wind speed magnitude and increases with extreme velocity changes and with higher wind speeds, resulting in a root-mean-square error (RMSE) of less than 0.2 m s−1 for steady wind speeds. Applying the calibration coefficients from one UAS to others within the fleet results in comparable accuracies. Flights in gusts of different strengths yield an RMSE of up to 0.6 m s−1. The maximal RMSE occurs in the most extreme velocity steps (i.e., a lower speed of 5 m s−1 and an amplitude of 10 m s−1) and exceeds 1.3 m s−1. For variances below approx. 0.5 and 0.3 m2 s−2, the maximal resolvable frequencies of the turbulence are about 2 and 1 Hz, respectively. The results indicate successful calibration but with susceptibility to high AoSs in high wind speeds, no necessity for wind tunnel calibration for individual UASs, and the need for further research regarding turbulence analysis.

Sub Miniature Kiel Probe for Total Pressure Measurements in Three Dimensional Boundary Layers

The design, fabrication and calibration details of a sub miniature Kiel probe for three-dimensional boundary layer measurements are presented in this paper. The probe has a nominal measurement dimension of 0.3 mm and a shroud size of 0.7 mm in the boundary layer direction thus minimizing spatial and flow gradient errors. The probe is calibrated in a calibration tunnel at a velocity of 50 m/s in the yaw and pitch angle ranges of ± 45° and ± 25° at 5° interval respectively. The non-dimensional pressure measured by the probe is plotted as contours. The non-dimensional pressure has a value within ± 1% of total pressure in the yaw and pitch angle ranges of ± 40° and ± 15° respectively. The probe is used to measure total pressure at the exit of a centrifugal impeller at four volume flows. The total pressure measured is found to follow expected trends.

Non-nulling protocols for fast, accurate, 3-D velocity measurements in stacks

ABSTRACT The authors present protocols for making fast, accurate, 3D velocity measurements in the stacks of coal-fired power plants. The measurements are traceable to internationally-recognized standards; therefore, they provide a rigorous basis for measuring and/or regulating the emissions from stacks. The authors used novel, five-hole, hemispherical, differential-pressure probes optimized for non-nulling (no-probe rotation) measurements. The probes resist plugging from ash and water droplets. Integrating the differential pressures for only 5 seconds determined the axial velocity V a with an expanded relative uncertainty U r(V a) ≤ 2% of the axial velocity at the probe’s location, the flow’s pitch (α) and yaw (β) angles with expanded uncertainties U(α) = U(β) = 1 °, and the static pressure p s with U r(p s) = 0.1% of the static pressure. This accuracy was achieved 1) by calibrating each probe in a wind tunnel at 130, strategically-chosen values of (V a, α, β) spanning the conditions found in the majority of stacks (|α| ≤ 20 °; |β| ≤ 40 °; 4.5 m/s ≤ V a ≤27 m/s), and 2) by using a long-forgotten definition of the pseudo-dynamic pressure that scales with the dynamic pressure. The resulting calibration functions span the probe-diameter Reynolds number range from 7,600 to 45,000. Implications: The continuous emissions monitoring systems (CEMS) that measure the flue gas flow rate in coal-fired power plant smokestacks are calibrated (at least) annually by a velocity profiling method. The stack axial velocity profile is measured by traversing S-type pitot probes (or one of the other EPA-sanctioned pitot probes) across two orthogonal, diametric chords in the stack cross-section. The average area-weighted axial velocity calculated from the pitot traverse quantifies the accuracy of the CEMS flow monitor. Therefore, the flow measurement accuracy of coal-fired power plants greenhouse gas (GHG) emissions depends on the accuracy of pitot probe velocity measurements. Coal-fired power plants overwhelmingly calibrate CEMS flow monitors using S-type pitot probes. Almost always, stack testers measure the velocity without rotating or nulling the probe (i.e., the non-nulling method). These 1D non-nulling velocity measurements take significantly less time than the corresponding 2D nulling measurements (or 3D nulling measurements for other probe types). However, the accuracy of the 1D non-nulling velocity measurements made using S-type probes depends on the pitch and yaw angles of the flow. Measured axial velocities are accurate at pitch and yaw angles near zero, but the accuracy degrades at larger pitch and yaw angles. The authors developed a 5-hole hemispherical pitot probe that accurately measures the velocity vector in coal-fired smokestacks without needing to rotate or null the probe. This non-nulling, 3D probe is designed with large diameter pressure ports to prevent water droplets (or particulates) from obstructing its pressure ports when applied in stack flow measurement applications. This manuscript presents a wind tunnel calibration procedure to determine the non-nulling calibration curves for 1) dynamic pressure; 2) pitch angle; 3) yaw angle; and 4) static pressure. These calibration curves are used to determine axial velocities from 6 m/s to 27 m/s, yaw angles between ±40°, and pitch angles between ±20°. The uncertainties at the 95% confidence limit for axial velocity, yaw angle, and pitch angle are 2% (or less), 1°, and 1°, respectively. Therefore, in contrast to existing EPA-sanctioned probes, the non-nulling hemispherical probe provides fast, low uncertainty velocity measurements independent of the pitch and yaw angles of the stack flow.

Calibration of Multi Hole Pressure Probes for Three Dimensional Flow Measurements in Subsonic Flow*

The calibration of two multi hole pressure probes with four and five pressure holes are presented at three Mach numbers, viz. M=0.3, 0.4 and 0.5. The calibration was carried out in a subsonic calibration tunnel in yaw angle and pitch angle range of ± 30° at 5° interval. Calibration curves are presented and compared at the three Mach numbers. Calibration data at one Mach number are used as calibration data and calibration data at other Mach numbers are used as measured data to find the flow parameters namely, total pressure and static pressure and flow yaw angle and pitch angle using a lookup table method at these Mach numbers. The interpolation errors are small when the yaw angle and pitch angle range is from -20° to 20° for the four hole probe and from -15° to 15° for the five hole probe. Mach number effects on the flow measurements can be incorporated using the iterative method presented. This method is used to obtain flow parameters in the wake of a steam turbine rotor tip cascade blade. The differences in the obtained values using calibration coefficients at three Mach numbers are found to be negligible.

Temperature and pressure effects on the response behavior of anemometers

Abstract Cup anemometers are within the most used wind speed sensors for the wind energy industry. Wind tunnel calibrations under controlled conditions are required, but during operation uncontrolled environmental conditions occur. This is accounted for in the IEC 61400-50-1:2022 international wind measurements standard, which specifies sensor classification based on their response to external conditions, due to the influence parameters turbulence, air temperature, density, and upflow angle. Temperature and density effects are not covered appropriately in the IEC 61400-50-1:2022, since it assumes that air temperature only influences the bearing friction of a cup anemometer. No guidance is provided on evaluating variations in density, which depends on temperature and pressure. To investigate this, two cup anemometers are measured in Deutsche WindGuard’s Climatic Wind Tunnel, where density is changed by varying pressure and temperature independently. The results show that the sensor’s response to temperature can have other effects than an increase in ball bearing friction. Using pressure or temperature to modify density can even cause opposing results. Hence, varying temperatures and pressures independently is crucial to characterize a sensor’s response. The results correspond to cup anemometers, but the methodology is applicable on all sensors.

CALIBRATION OF PHOTOGRAMMETRIC SYSTEM FOR 3D MEASUREMENTS IN INACCESSIBLE MULTIMEDIA WORKING SPACE

Abstract. Hydrodynamic tunnel has proved to be an effective mean for studying aerodynamic processes using scaled models of real aircrafts. The specificity of study in a hydrodynamic tunnel requires to apply non-contact measuring techniques, such as photogrammetry, for retrieving information on geometrical characteristics of the flow. So reliable calibration of photogrammetric system is a key element for trustworthy analysis of flow behaviour. For 3D measurements in a hydrodynamic tunnel calibration technique must account for refraction effects at optical media interfaces. But often the design of a hydrodynamic tunnel does not allow to perform standard calibration procedure based on image acquisition of a special test field, placed in the working space of the measuring system. The presented study addresses this problem – developing the technique for accurate photogrammetric calibration, for the case of the working space being inaccessible for placing there a test field. The developed calibration technique estimates parameters of interior orientation of the photogrammetric system and parameters of multimedia optical environment by special preliminary procedure, that allows to obtain accurate 3D measurements during experiments in hydrodynamic tunnel. Experimental evaluation of the developed technique demonstrated high accuracy of photogrammetric 3D measurements.

Comparison of different droplet measurement techniques in the Braunschweig Icing Wind Tunnel

Abstract. The generation, transport and characterization of supercooled droplets in multiphase wind tunnel test facilities is of great importance for conducting icing experiments and to better understand cloud microphysical processes such as coalescence, ice nucleation, accretion and riming. To this end, a spray system has been developed, tested and calibrated in the Braunschweig Icing Wind Tunnel. Liquid droplets in the size range of 1 to 150 µm produced by pneumatic atomizers were accelerated to velocities between 10 and 40 m s−1 and supercooled to temperatures between 0 and −20 ∘C. Thereby, liquid water contents between 0.07 and 2.5 g m−3 were obtained in the test section. The wind tunnel conditions were stable and reproducible within 3 % standard variation for median volumetric diameter (MVD) and 7 % standard deviation for liquid water content (LWC). Different instruments were integrated in the icing wind tunnel measuring the particle size distribution (PSD), MVD and LWC. Phase Doppler interferometry (PDI), laser spectroscopy with a fast cloud droplet probe (FCDP) and shadowgraphy were systematically compared for present wind tunnel conditions. MVDs measured with the three instruments agreed within 15 % in the range between 8 and 35 µm and showed high coefficients of determination (R2) of 0.985 for FCDP and 0.799 for shadowgraphy with respect to PDI data. Between 35 and 56 µm MVD, the shadowgraphy data exhibit a low bias with respect to PDI. The instruments' trends and biases for selected droplet conditions are discussed. LWCs determined from mass flow calculations in the range of 0.07–1.5 g m−3 are compared to measurements of the bulk phase rotating cylinder technique (RCT) and the above-mentioned single-particle instruments. For RCT, agreement with the mass flow calculations of approximately 20 % in LWC was achieved. For PDI 84 % of measurement points with LWC<0.5 g m−3 agree with mass flow calculations within a range of ±0.1 g m−3. Using the different techniques, a comprehensive wind tunnel calibration for supercooled droplets was achieved, which is a prerequisite for providing well-characterized liquid cloud conditions for icing tests for aerospace, wind turbines and power networks.

Double S-type Pitot Tube for velocity field study of fire whirls

In this paper we present a pressure measurement instrument based on the S-type Pitot tube modified to measure the two velocity components of a high temperature flow assuming that the flow is locally two-dimensional. The development of this new device, which we designate as the Double S-type Pitot Tube, is related to the difficulty and the lack of precision of measurements with a standard S-type Pitot tube in flows with unknown directions like the case of fire whirls in laboratory experiments. The design construction and calibration method of the device are described. The pitch angle of the flow and the velocity coefficients of the probe are analysed experimentally in a wind tunnel calibration as well as the associated errors. The use of this sensor in a fire whirl laboratory test is shown and the results are compared with those of simple S-type Pitot tubes in the same test. The obtained results show the applicability and better performance of the novel device.

Design and analysis of five probe flow analyser for subsonic and supersonic wind tunnel calibration

The flow angularity in a wind tunnel plays a major role in test section when testing models. The models are being tested at a mixture of flow velocity. Usually a subsonic wind tunnel is calibrated using a normal Pitot tube and supersonic wind tunnels with high efficiency probes. The calibration of a wind tunnel includes determining the Mach number range ad pressure range throughout the test section of the flow throughout the pattern of operating velocity. In the analysis it is noted that the sensitivities of the calibrating instruments are maximum when it is either cone or wedge shaped. When the wedge or cone angles are maximum, more accurate results are also obtained, but it’s not possible to have a maximum angle cone or wedge because of the detached wave and tunnel blockage factors. Hence in order to overcome this difficulties in measurement, a five probe flow analyzer has been designed. The five probe flow analyzer is used to determine the wind tunnel test section parameters like flow angularity, Pitot pressures, static pressures, wave angles, and the presence of test section noise. Over to these parameter, the stagnation states can also be determined using this analyzer. The proposed model is designed by getting optimum solutions from previous analysis and the existing data by considering all the aerodynamic and mechanical loading. This instrument designed is to be tested experimentally after carrying two and three dimensional computational analysis for Mach number ranging from 0.5 of 3. Also it is designed to fit successfully for 0.3m and 0.6m test section wind tunnel to obtain reasonably merging solution with theoretical and experimental results.

Amplification and structure of streamwise-velocity fluctuations in compression-corner shock-wave/turbulent boundary-layer interactions

In this work, we study the effect of the compression-corner angle on the streamwise turbulent kinetic energy (sTKE) and structure in Mach 2.8 flow. Krypton tagging velocimetry (KTV) is used to investigate the incoming turbulent boundary layer and flow over$8^{\circ }$,$16^{\circ }$,$24^{\circ }$and$32^{\circ }$compression corners. The experiments were performed in a 99 %$\text{N}_{2}$and 1 % Kr gas mixture in the Arnold Engineering Development Complex (AEDC) Mach 3 Calibration Tunnel (M3CT) at$Re_{\unicode[STIX]{x1D6E9}}=1750$. A figure of merit is defined as the wall-normal integrated sTKE ($\overline{\text{sTKE}}$), which is designed to identify turbulence amplification by accounting for the root-mean-squared (r.m.s.) velocity fluctuations and shear-layer width for the different geometries. We observe that the$\overline{\text{sTKE}}$increases as an exponential with the compression-corner angle near the root when normalized by the boundary-layer value. Additionally, snapshot proper orthogonal decomposition (POD) is applied to the KTV results to investigate the structure of the flow. From the POD results, we extract the dominant flow structures and compare each case by presenting mean-velocity maps that correspond to the largest positive and negative POD mode coefficients. Finally, the POD spectrum reveals an inertial range common to the boundary-layer and each compression-corner flow that is present after the first${\approx}10$dominant POD modes.

OVLI-TA: An Unmanned Aerial System for Measuring Profiles and Turbulence in the Atmospheric Boundary Layer

In recent years, we developed a small, unmanned aerial system (UAS) called OVLI-TA (Objet Volant Leger Instrumenté–Turbulence Atmosphérique) dedicated to atmospheric boundary layer research, in Toulouse (France). The device has a wingspan of 2.60 m and weighed 3.5 kg, including payload. It was essentially developed to investigate turbulence in a way complementary to other existing measurement systems, such as instrumented towers/masts. OVLI-TA’s instrumental package includes a 5-hole probe on the nose of the airplane to measure attack and sideslip angles, a Pitot probe to measure static pressure, a fast inertial measurement unit, a GPS receiver, as well as temperature and moisture sensors in specific housings. In addition, the Pixhawk autopilot is used for autonomous flights. OVLI-TA is capable of profiling wind speed, wind direction, temperature, and humidity up to 1 km altitude, in addition to measuring turbulence. After wind tunnel calibrations, flight tests were conducted in March 2016 in Lannemezan (France), where there is a 60-m tower equipped with turbulence sensors. In July 2016, OVLI-TA participated in the international project DACCIWA (Dynamics-Aerosol-Chemistry-Clouds Interactions in West Africa), in Benin. Comparisons of the OVLI-TA observations with both the 60 m tower measurements and the radiosonde profiles showed good agreement for the mean values of wind, temperature, humidity, and turbulence parameters. Moreover, it validated the capacity of the drone to sample wind fluctuations up to a frequency of around 10 Hz, which corresponds to a spatial resolution of the order of 1 m.

Savremeni pristup merenja i procena kvaliteta strujanja u podzvučnom aerotunelu

The requirements for the accuracy of measurements in a wind tunnel test become more and more severe while the complexity of the test increases. In an environment of reduced time available for wind tunnel test and increasing test costs, it is important that the accurate calibrations and verifications of all components of the measurement chain in a wind tunnel facility are established, maintained and statistically controlled through prolonged periods of time. The paper presents the efforts undertaken to establish and maintain a system of control of the quality of measurements in the T-35 4.4 m × 3.2 m low-speed wind tunnel of the Military Technical Institute in Belgrade. The assurance of the quality of measurement in this facility is based on ensuring the quality of three main constituents: the calibration of the test section of the wind tunnel, the calibration of the instrumentation used, and the periodic tests of the standard wind tunnel models. Sample results from relevant wind tunnel calibration tests are presented and compared with the results from other facilities. The tests confirmed a good overall quality of the facility, and that the achieved quality level has to be maintained, periodically checked and systematically documented.

A compact in-blade five hole pressure probe for local inflow study on a horizontal axis wind turbine

Understanding local inflow conditions on a wind turbine blade on an operating wind turbine can further understanding of aerodynamic variations and help predict loads on the turbine. Turbine blades are generally designed with a two-dimensional steady approach, however the real wind conditions are highly three-dimensional (3D) and unsteady. Detailed measurements are not common for validating aerodynamic models. The aim of this theoretical and experimental study is to build, calibrate, install and test a compact in-blade five hole pressure probe system to be used to retrieve these measurements. Wind tunnel calibration of the five hole pressure probe has been successfully completed using an automated traversing system over a ±45° range, with 5° increments. Error analysis showed that the multi-zone pressure coefficient data reduction approach is the most suitable for this application. This approach not only extends the measurable local inflow angles up to ±70°, but also it allows any reference pressure for differential pressure readings. A new data acquisition system (DAQ) internal to a rotating small wind turbine blade section was developed. Space limitations resulted in a custom built DAQ of very contained dimensions. This included, among others, five pressure transducers on a printed circuit board, a 16 bit analog to digital converter, an Arduino microcontroller, and a Bluetooth transceiver to transmit the data wirelessly to the main computer. The new blade section was designed and 3D-printed in such a way that the DAQ instrumentation could be easily accessed and, at the same time, had an acceptable structural solidity. A series of tests were conducted on a 3.4 m diameter wind turbine in a large scale wind tunnel in order to assess the correct functioning of the probe system. As expected, the inflow measurement obtained while the turbine was operating under yawed conditions showed a periodically oscillating inflow vector. The period of this variation was the same as the period of the rotor rotation.

Krypton tagging velocimetry in a turbulent Mach 2.7 boundary layer

The krypton tagging velocimetry (KTV) technique is applied to the turbulent boundary layer on the wall of the “Mach 3 Calibration Tunnel” at Arnold Engineering Development Complex (AEDC) White Oak. Profiles of velocity were measured with KTV and Pitot-pressure probes in the Mach 2.7 turbulent boundary layer comprised of 99 % $$\hbox {N}_{2}$$ /1 % Kr at momentum-thickness Reynolds numbers of $${Re}_{\varTheta }= 800, 1400$$ , and 2400. Agreement between the KTV- and Pitot-derived velocity profiles is excellent. The KTV and Pitot velocity data follow the law of the wall in the logarithmic region with application of the Van Driest I transformation. The velocity data are analyzed in the outer region of the boundary layer with the law of the wake and a velocity-defect law. KTV-derived streamwise velocity fluctuation measurements are reported and are consistent with data from the literature. To enable near-wall measurement with KTV ( $$y/\delta \approx $$ 0.1–0.2), an 800-nm longpass filter was used to block the 760.2-nm read-laser pulse. With the longpass filter, the 819.0-nm emission from the re-excited Kr can be imaged to track the displacement of the metastable tracer without imaging the reflection and scatter from the read-laser off of solid surfaces. To operate the Mach 3 AEDC Calibration Tunnel at several discrete unit Reynolds numbers, a modification was required and is described herein.

Miniature Four Hole Probe for Three Dimensional Boundary Layer Measurements

The design, fabrication and calibration details of a miniature four hole probe for three-dimensional boundary layer measurements are presented in this paper. The probe has a nominal measuring area of 1 mm2 and has a nominal dimension of 0.4 mm in the boundary layer direction thus minimizing pressure and velocity gradient errors and wall vicinity errors. The probe is calibrated in an open jet calibration tunnel at a velocity of 50 m/s in the yaw and pitch angle range of + 40O at 5O interval. The calibration coefficients are defined, calculated and presented. The sensitivity of the calibration coefficients is also calculated and presented.

A Miniature Four-Hole Probe for Measurement of Three-Dimensional Flow with Large Gradients

A miniature four-hole probe with a sensing area of 1.284 mm2to minimise the measurement errors due to the large pressure and velocity gradients that occur in highly three-dimensional turbomachinery flows is designed, fabricated, calibrated, and validated. The probe has good spatial resolution in two directions, thus minimising spatial and flow gradient errors. The probe is calibrated in an open jet calibration tunnel at a velocity of 50 m/s in yaw and pitch angles range of ±40 degrees with an interval of 5 degrees. The calibration coefficients are defined, determined, and presented. Sensitivity coefficients are also calculated and presented. A lookup table method is used to determine the four unknown quantities, namely, total and static pressures and flow angles. The maximum absolute errors in yaw and pitch angles are 2.4 and 1.3 deg., respectively. The maximum absolute errors in total, static, and dynamic pressures are 3.4, 3.9, and 4.9% of the dynamic pressures, respectively. Measurements made with this probe, a conventional five-hole probe and a miniature Pitot probe across a calibration section, demonstrated that the errors due to gradient and surface proximity for this probe are considerably reduced compared to the five-hole probe.

New Methodology for Wind Tunnel Calibration Using Neural Networks - EGD Approach

One of the hardest tasks involving wind tunnel characterization is to determine the air-flow condition inside the test section. The Log-Tchebycheff method and the Equal Area method allow calculation of local velocities from measured differential pressures on rectangular and circular ducts. However, these two standard methods for air flow measurement are limited by the number of accurate pressure readings by the Pitot tube. In this paper, a new approach is presented for wind tunnel calibrations. This approach is based on a limited number of dynamic pressure measurements and a predictive technique using Neural Network (NN). To optimize the NN, the extended great deluge (EGD) algorithm is used. Wind tunnel testing involves a large number of variables such as wind direction, velocity, rate flow, turbulence characteristics, temperature variation and pressure distribution on airfoils. NN has the advantage that multilayer perceptron neural networks can describe a 3D flow area with a small amount of experimental data, fewer numbers of iterations and less computation time per iteration. The Fluent results are used to train and optimize the proposed NN approach. The validation of this new approach is achieved by experimental tests using the wind tunnel Price-Paidoussis of LARCASE laboratory. This wind tunnel has two test chambers. The main chamber with a section Height, Width and Length equal to 0.62 x 0.91 x 1.83 meter respectively that provides a speed ranging from 0 to 30 m/s and a second chamber test with a section Height, Width and Length equal to 0.31 x 0.61 x 1.22 meters respectively that provides a speed from 0 to 60 m/s.

Experimental results and numerical simulations for transonic flow over the ONERA M4R model

This paper presents a comparison between experimental results of transonic flow over the ONERA M4R calibration model obtained in the INCAS Trisonic wind tunnel and the numerical results. The first purpose, emphasized in this paper is to compare and validate the computational fluid dynamics (CFD) techniques for internal transonic flows and to try to find the most suitable numerical methodology for these flows in both accuracy and computational resources. The second purpose is to develop a general method in experimental data correction and flight Reynolds extrapolation, using numerical simulations for both global and local pressure coefficients, as a replacement for the classical vortex lattices based method. That will be developed in a future paper. Besides the computational work, the periodic wind tunnel calibration is required as a quality insurance operation and a numerical model is developed such that future hardware modifications to be included and their impact to be properly considered.

Recalibration of Flush Air Data System (FADS) on Pressure Port/Sensor Failures

Flush Air Data sensing System (FADS) forms a mission critical sub system in future reusable space transportation systems. FADS makes use of surface pressure measurements from the nose cap of the vehicle for deriving the air data parameters of the vehicle like angle of attack, angle of sideslip, Mach number, etc. These parameters are used by the control and guidance system of the vehicle for reentry flight management as well as for subsequent mission phases upto landing. The on board algorithm makes use of calibration coefficients derived from wind tunnel data to achieve better accuracy in the estimated air data parameters. In the event of faults in FADS due to port blockages or pressure sensor failures, recalibration is essential for achieving the desired accuracy of air data estimates. This paper describes recalibration of FADS using surface fit method in the event of pressure port blockage or sensor failures. The method is based on the storage of coefficients of a 4th order surface fit corresponding to the wind tunnel calibration data and recalibration using these polynomial coefficients.