Test Section Flow Research Articles

Design and evaluation of a high-speed aeroacoustic wind tunnel

The high-speed aeroacoustic wind tunnel (HSAWT) at Carleton University is a new facility commissioned with the purpose of facilitating experimental studies of turbulent boundary layer (TBL) induced surface pressure fluctuations. This research is primarily intended for applications related to aircraft cabin noise generation from structures exposed to high-speed flow. This open-jet, blowdown wind tunnel is a unique facility in Canada and one of a few aeroacoustic wind tunnels in the world capable of achieving speeds up to Mach 0.8. Flow is delivered from a nozzle with dimensions of 6.1 cm × 15 cm to a test section enclosed within an anechoic chamber with internal dimensions of 1.9 m × 0.88 m × 1.95 m. This study details the complete design methodology for all major wind tunnel components, including the numerical simulations performed in the validation of the designed components. Results of preliminary test section flow characterization and chamber background noise measurements are discussed. Finally, experimental results of the TBL surface pressure fluctuation spectral behavior developed over a flat test section plate are compared with established data and empirical models available in literature.

Experimental characterization of the transonic test section flow in a Ludwieg tube

A new Ludwieg tube for transonic testing has been put into operation. For this, an existing shock tube has been modified to a Ludwieg tube. The ideal operating principle is described by theory and corresponding theoretical values are compared to experimental ones. Pressure histories as well as test section flow visualization demonstrate a better performance concerning flow quality and testing time compared to the former shock tube. Static as well as total pressure measurements have been performed within the test section. Pitot rake measurements show the homogeneity of the test section flow field. Additional boundary layer profile measurements give evidence of the temporal growth of the test section wall boundary layer. These results are compared with theoretical ones deduced from a theoretical approach for a boundary layer behind an expansion wave. Both, boundary layer and Pitot rake measurements allow to discuss the influence of a turbulent boundary layer on these measurements. Cookie cutters at the entrance to the test section act as boundary layer bleed which partially avoid the entering of the tube wall boundary layer into the test section. Their influence on the test section flow is discussed as well.

Analysis of subsonic wind tunnel with variation shape rectangular and octagonal on test section

The need for good design in the aerodynamics field required a wind tunnel design. The wind tunnel design required in this case is capable of generating laminar flow. In this research searched for wind tunnel models with rectangular and octagonal variations with objectives to generate laminar flow in the test section. The research method used numerical approach of CFD (Computational Fluid Dynamics) and manual analysis to analyze internal flow in test section. By CFD simulation results and manual analysis to generate laminar flow in the test section is a design that has an octagonal shape without filled for optimal design.

Inverse measurement of wall pressure field in flexible-wall wind tunnels using global wall deformation data

The Kevlar-wall anechoic wind tunnel offers great value to the aeroacoustics research community, affording the capability to make simultaneous aeroacoustic and aerodynamic measurements. While the aeroacoustic potential of the Kevlar-wall test section is already being leveraged, the aerodynamic capability of these test sections is still to be fully realized. The flexibility of the Kevlar walls suggests the possibility that the internal test section flow may be characterized by precisely measuring small deflections of the flexible walls. Treating the Kevlar fabric walls as tensioned membranes with known pre-tension and material properties, an inverse stress problem arises where the pressure distribution over the wall is sought as a function of the measured wall deflection. Experimental wall deformations produced by the wind loading of an airfoil model are measured using digital image correlation and subsequently projected onto polynomial basis functions which have been formulated to mitigate the impact of measurement noise based on a finite-element study. Inserting analytic derivatives of the basis functions into the equilibrium relations for a membrane, full-field pressure distributions across the Kevlar walls are computed. These inversely calculated pressures, after being validated against an independent measurement technique, can then be integrated along the length of the test section to give the sectional lift of the airfoil. Notably, these first-time results are achieved with a non-contact technique and in an anechoic environment.

WITHDRAWN: Thermal-hydraulic test loop identification using nonlinear method; an approach to mathematical modeling of the energy system

In this study, two mathematical identification methods, used to identify the thermodynamic parameters of Columbia University 1.5 MW test loop as a low energy system. This test loop is a scaled loop of Savanah River Site (SRS) reactors and the experiment was the onset of flow instability experiment. Recursive least squares (RLS) algorithm and a non-linear (NL) algorithm are the two algorithms used for identification. Test section flow rate and pressure drop considered as the single input and the single output of the system respectively. 600 data set entries are the input used to calculate the parameter vectors and 190 data set entries used for evaluation of the models. For conservative calculations, the test data selected over the range of the training data. The system has been identified in the best manner using both methods with a calculation error less than 1%. By comparing calculated parameters with the measured data it can be concluded that non-linear algorithm has more speed to determine the coefficients of the proposed equations and can be used as a reactor transient monitoring tool like a sensor. However, the RLS algorithm properly identified the system parameters via the linear method, too.

Measurements of translational slug velocity and slug length using an image processing technique

Slug flow is a common flow regime that occurs in various industries, such as oil, gas, and power generation industries. In this study, the mean slug translational velocity and slug liquid length were measured using Phantom 9.2 software and an image processing analysis technique. The adopted image processing technique involved the analysis of video frames recorded from a high-speed camera (Phantom 9.2) in a horizontal transparent pipe using a combination of the approximate median method and blob analysis, along with an additional morphological process for detecting and segregating individual slugs. The experimental data were obtained from a designed two-phase flow test section, in which sets of superficial water and air velocities were selected to generate numerous slug flows. A good agreement with a maximum deviation of 6.7% between the estimated slug parameters from the adopted technique and the Phantom cine view controller software was achieved. Additionally, the developed technique provided precise results with a high processing speed of 10 frames per second.

Development of an anechoic wind tunnel

The development of an anechoic wind tunnel is presented. The test section walls of a low-speed open-circuit wind tunnel have been acoustically treated in order to simulate an acoustically free field environment with forward flight. The dimensions of the test section are 0.86 m wide by 0.56 m tall and 1.32 m long. The four walls of the test section are lined with pretensioned Kevlar panels that permit the transmission of sound with less than 2 dB of attenuation. The top and bottom walls of the test section sandwich 4-in. thick acoustic foam between the pretensioned Kevlar and a wooden frame. The side walls of the test section consists of pretensioned Kevlar screens that separate the test section flow from adjacent anechoic chambers. In this fashion, the acoustic measuring equipment is not subjected to the flow inside the test section. Noise sources are modeled with a small loudspeaker that is connected to a signal generator and acoustic measurements are taken with quarter-inch condenser microphones. Prelim...

The influence of the equivalent hydraulic diameter on the pressure drop prediction of annular test section

The flow behaviour and the pressure drop throughout an annular flow test section was investigated in order to evaluate and justify the reliability of experimental flow loop for wax deposition studies. The specific objective of the present paper is to assess and highlight the influence of the equivalent diameter method on the analysis of the hydrodynamic behaviour of the flow and the pressure drop throughout the annular test section. The test section has annular shape of 3 m length with three flow passages, namely; outer thermal control jacket, oil annular flow and inner pipe flow of a coolant. The oil annular flow has internal and external diameters of 0.0422 m and 0.0801 m, respectively. Oil was re-circulated in the annular passage while a cold water-glycol mixture was re-circulated in the inner pipe counter currently to the oil flow. The experiments were carried out at oil Reynolds number range of 2000 to 17000, covering laminar, transition and turbulent flow regimes. Four different methods of equivalent diameter of the annulus have been considered in this hydraulic analysis. The correction factor model for frictional pressure drop was also considered in the investigations. All methods addressed the high deviation of the prediction from the experimental data, which justified the need of a suitable pressure prediction correlation for the annular test section. The conventional hydraulic diameter method is a convenient substitute for characterizing physical dimension of a non-circular duct, and it leads to fairly good correlation between turbulent fluid flow and heat transfer characteristic of annular ducts.

English

This research work presents the experimental results of the effect of polypropylene beads' concentrations in waterbased mud on wellbore cleaning. A comparative study of cuttings transport performance (CTP) of water-based mud and water-based mud with polypropylene beads were carried out at different hole angles of 0°, 30°, 60°. 75° and 90° in a 13 ft (3.96 m) acrylic concentric annulus flow test section, having a 2 in (50.8 mm) casing ID and a fixed 0.79 in (20 mm) inner pipe OD. A total of 100 runs had been accomplished using fine sands (from Tanjung Balau, Johor Bahru, Malaysia), of size ranging from 5/127-6/127 (1.0-1.2 mm) and density 2.4 g/cc (2400 kg/m3), with the mud density and viscosity maintained at 9 ppg (1078 kg/m3) and 5 cp (0.005 Pa.s), respectively, in a flow velocity of 2.1 ft/s (0.64 m/s). Polypropylene beads used in this study have the following properties: 290 kg/cm2 of tensile strength at yield, 0.86 g/cc (860 kg/m3) density, 4 mm (20/127) size, 82 R scale Rockwell hardness, 13,500 kg/cm2 flexural modulus, 85°C heat deflection temperature at 4.6 kg/cm2, 4 g/10 min melt flow rate at 230°C and spherical in shape. The experimental findings showed that commingling the basic mud with polypropylene beads has successfully introduced a buoyant force which was found to have improved the cuttings transport performance by more than 10% when weight concentration of the polypropylene beads was increased to 1.5% as compared with the performance obtained from the basic water-based mud. The improvement of cuttings transport performance was found to be more significant in a vertical hole.

Experimental characterization of vertical gas–liquid pipe flow for annular and liquid loading conditions using dual Wire-Mesh Sensor

In gas well production, liquid is produced in two forms, droplets entrained in the gas core and liquid film flowing on the tubing wall. For most of the gas well life cycle, the predominant flow pattern is annular flow. As gas wells mature, the produced gas flow rate reduces decreasing the liquid carrying capability initiating the condition where the liquid film is unstable and flow pattern changes from fully cocurrent annular flow to partially cocurrent annular flow. The measurement and visualization of annular flow and liquid loading characteristics is of great importance from a technical point of view for process control or from a theoretical point of view for the improvement and validation of current modeling approaches. In this experimental investigation, a Wire-Mesh technique based on conductance measurements was applied to enhance the understanding of the air-water flow in vertical pipes. The flow test section consisting of a 76mm ID pipe, 18m long was employed to generate annular flow and liquid loading at low pressure conditions. A 16×16 wire configuration sensor is used to determine the void fraction within the cross-section of the pipe. Data sets were collected with a sampling frequency of 10,000Hz. Physical flow parameters were extracted based on processed raw measured data obtained by the sensors using signal processing. In this work, the principle of Wire-Mesh Sensors and the methodology of flow parameter extraction are described. From the obtained raw data, time series of void fraction, mean local void fraction distribution, characteristic frequencies and structure velocities are determined for different superficial liquid and gas velocities that ranged from 0.005 to 0.1m/s and from 10 to 40m/s, respectively. In order to investigate dependence of liquid loading phenomenon on viscosity, three different liquid viscosities were used. Results from the Wire-Mesh Sensors are compared with results obtained from previous experimental work using Quick Closing Valves and existing modeling approaches available in the literature.

Experimental Investigation of Horizontal Gas–Liquid Stratified and Annular Flow Using Wire-Mesh Sensor

Stratified and annular gas–liquid flow patterns are commonly encountered in many industrial applications, such as oil and gas transportation pipelines, heat exchangers, and process equipment. The measurement and visualization of two-phase flow characteristics are of great importance as two-phase flows persist in many fluids engineering applications. A wire-mesh sensor (WMS) technique based on conductance measurements has been applied to investigate two-phase horizontal pipe flow. The horizontal flow test section consisting of a 76.2 mm ID pipe, 18 m long was employed to generate stratified and annular flow conditions. Two 16 × 16 wire configuration sensors, installed 17 m from the inlet of the test section, are used to determine the void fraction within the cross section of the pipe and determine interface velocities between the gas and liquid. These physical flow parameters were extracted using signal processing and cross-correlation techniques. In this work, the principle of WMS and the methodology of flow parameter extraction are described. From the obtained raw data time series of void fraction, cross-sectional mean void fraction, time averaged void fraction profiles, interfacial structures, and velocities of the periodic structures are determined for different liquid and gas superficial velocities that ranged from 0.03 m/s to 0.2 m/s and from 9 m/s to 34 m/s, respectively. The effects of liquid viscosity on the measured parameters have also been investigated using three different viscosities.

Experimental investigation of the effect of 90° standard elbow on horizontal gas–liquid stratified and annular flow characteristics using dual wire-mesh sensors

Fluid flowing through pipelines often encounters fittings such as elbows. Although it is true that two-phase flow patterns observed in elbows are qualitatively the same as those seen in straight pipes, the presence of a pipe elbow can modify relative positions and local velocities of the two phases as they are subjected to forces in addition to those encountered in a straight pipe. That redistribution can affect pressure drop values, chemical inhibitor concentration and distribution to the top of the pipe, as well as the erosion pattern occurring from solid particles such as sand that is entrained in oil and gas transportation pipelines. In this work, a wire-mesh sensor technique based on conductance measurements of void fraction was applied to investigate two-phase pipe flow through a standard elbow. The horizontal flow test section, consisting of a 76.2mm ID, 18m long pipe, was employed to generate stratified-wavy and annular flow conditions. Two 16×16 wire-mesh configuration sensors were positioned either 0.9m upstream or 0.6m downstream of the bend. The experiments were conducted at superficial liquid velocities equal to 0.03m/s and 0.2m/s and superficial gas velocities that ranged from 9m/s to 34m/s. The effects of liquid viscosity on the measured parameters are also investigated using two different viscosities of 1and 10cP. Stratified–slug transition, stratified wavy and annular flow patterns were observed visually in the clear section placed upstream of the wire-mesh sensors. Analysis of time series void fraction data from the dual wire-mesh sensors allows the determination of mean void fraction, local time average void fraction distribution, liquid phase distribution around the tube periphery, interfacial structure velocities, as well as probability density function characteristic signatures within the cross-section of pipe before and after the elbow. The results indicate that the distribution of gas and liquid phases and interfacial velocities are significantly altered even 20 diameters downstream of the elbow.

A validated design methodology for a closed-loop subsonic wind tunnel

A systematic investigation into the design and simulation of flow parameters in a closed-loop wind tunnel was carried out using Computational Fluid Dynamics (CFD). The analytical model for estimating pressure losses were directed as input boundary conditions. Full-scale model of the entire wind tunnel was considered instead of the conventional approach, in which only test section flow is simulated. This allowed for optimisation of flow quality not only in the test section but also the flow in the entire circuit. Analysis of the guide vane configurations showed that test section flow quality was more affected by flow conditions in upstream than downstream sections. Hence, special attention must be given while designing the vanes at upstream turns particularly corners in line with the test section. Validation of the test section with block model showed that CFD was able to replicate wind tunnel measurements of velocity, turbulence intensity and pressure coefficient with error below 10%.

Influence of Regulating Seam on Aerodynamic Characteristics of Virtual Wind Tunnel

A digital car model was taken as study object, and the influence of the regulating seam to an open type automobile wind tunnel was discussed by comparing simulation results with test data.The results show that the regulating seam changes the flow field around the collector, reduces the size of unsteady flow field and the flow in test section is uniformed better. Thus, the regulating seam shouldn’t be removed when simplifying the wind tunnel model in the simulation. This conclusion will provide theoretical basis and data support for better virtual reproduction and numerical simulation of a wind tunnel.

Image processing techniques for high-speed videometry in horizontal two-phase slug flows

Two-phase flow measurements are very common in industrial applications especially in oil and gas areas. Although some works in image segmentation have analyzed gas–liquid slug flow along vertical pipes, few approaches have focused on horizontal experiments. In such conditions, the detection of the Taylor bubble is challenging due the great amount of small bubbles in the slug area and, thus, requires a special treatment in order to separate gas from liquid phases. This article describes a new technique that automatically estimates bubble parameters (e.g. frequency, dimension and velocity) through video analysis of high-speed camera measurements in horizontal pipes. Experimental data were obtained from a flow test section where slug flows were generated under controlled conditions. Image processing techniques such as watershed segmentation, top-hat filtering and H-minima transform were applied to detect and estimate bubble contour and velocities from the observed images. Finally, the estimated parameters were compared to theoretical predictions, showing good agreement and indicating that the proposed technique is a powerful tool in the investigation of two-phase flow.

A fluid dynamic gauging device for measuring fouling deposit thickness in opaque liquids at elevated temperature and pressure

We report proof-of-concept results for a fluid dynamic gauging (FDG) device for measuring the thickness and strength of soft solid fouling layers immersed in an opaque liquid in situ and in real time at elevated pressures and temperatures. The device reported here is configured to make measurements on the inner rod of an annular flow test section but the concept is generic. Data are presented from tests using mineral oil at temperatures and pressures up to 140°C and 10bara, respectively. Problems with the prototype hardware prevented testing up to the design limits of 270°C and 30bara. The practical working range of the gauge, i.e. 0.05<h/dt<0.25, proved to be unaffected by the pressure and temperature. h is the nozzle-surface clearance and dt the nozzle throat diameter. At smaller h/dt values the pressure drop across the nozzle is very high and this can serve as an alarm for close approach. When the Reynolds number at the throat, Ret, is less than 20 the range of discharge coefficient values (0-Cd∞) is small, with a maximum value dependent on Ret. A useful range of Cd∞ values is obtained when Ret>40. Computational fluid dynamics (CFD) simulations of the gauging flow in these quasi-static experiments (no bulk liquid flow) gave good agreement with experimental data for the cases tested. The CFD results showed that the low Ret regime is related to creeping flow in the nozzle. CFD calculations of the shear stress being imposed on the surface being gauged gave good agreement with an analytical model for flow between parallel discs, indicating that the latter can be used to estimate the maximum shear stress imposed by the gauging flow.

Linear Cascade Wind Tunnel Testing of Supersonic Inflow and Outflow Turbine Blades (Test Section Design and Flow Visualization Using Schlieren Techniques)

Linear Cascade Wind Tunnel Testing of Supersonic Inflow and Outflow Turbine Blades (Test Section Design and Flow Visualization Using Schlieren Techniques)

Shear Layer Time-Delay Correction Using a Non-Intrusive Acoustic Point Source

Microphone array processing algorithms often assume straight-line source-to-observer wave propagation. However, when the microphone array is placed outside an open-jet test section, the presence of the shear layer refracts the acoustic waves and causes the wave propagation times to vary from a free-space model. With a known source location in space, the propagation time delay can be determined using Amiet's theoretical method. In this study, the effects of shear layer refraction are examined using a pulsed laser system to generate a plasma point source in space and time for several different test section flow speeds and configurations. An array of microphones is used to measure the pulse signal, allowing for the use of qualitative beamforming and quantitative timing analysis. Results indicate that Amiet's method properly accounts for planar shear layer refraction time delays within experimental uncertainty. This is true both when the source is in the inviscid core of the open-jet test section, as well as when the source is located in different model wakes of varying complexity. However, the method breaks down where the thin layer assumption fails, such as in the region where the tunnel test section's open jet interacts with the facility jet collector.

Prediction of total pressure characteristics in the settling chamber of a supersonic blowdown wind tunnel

AbstractOccurrence of transient starting and stopping loads during tests at high Mach numbers is one of the major problems in intermittent blowdown wind tunnels. It is believed that in order to overcome this problem, the wind tunnel could be started at a low Mach number and low stagnation pressure; the desired high Mach number condition could be reached by continuously changing the nozzle contour while synchronously increasing the stagnation pressure. After completing the tests, the nozzle could be brought back to the initial low Mach number accompanied by synchronous decrease in the stagnation pressure. In such a scenario, it is important to ensure that the pressure regulating valve (PRV) of the wind tunnel delivers and maintains a specified minimum stagnation pressure at any Mach number, so that supersonic breakdown of the test section flow does not occur. In this paper, the problem is formulated based on quasi-steady one-dimensional isentropic equations and numerically solved to predict the time histories of settling chamber pressure and storage tank pressure for a given trajectory of the opening of the PRV, as the Mach number is changed from Mach 1 to 4·0 continuously in four seconds and vice versa. The effects of rate of change of PRV open area and rate of change of Mach number on the stagnation pressure characteristics in the settling chamber and storage tank are predicted. The measured trajectories of the PRV in experiments in the NAL 0·6m transonic wind tunnel are used as input to the prediction program to validate the methodology. Predictions indicate that when the nozzle throat is changed from Mach 1 to 4 in four seconds, the settling chamber stagnation pressure rapidly builds up and approaches the pressure in the storage tank. Predictions show an alarming rise in free stream dynamic pressure during transition from Mach 1 to 4 and vice versa, which needs to be verified through measurements.

Heat transfer and pressure drop characteristics of suspensions of synthetic and wood pulp fibres in annular flow

Pressure drop and heat transfer data were obtained from a specially designed flow loop with an annular flow test section housing a coaxially located heating rod with a calming extension. The heating element was embedded in the central rod with thermocouples located just below the surface at the heater in the flow direction. The pressure drop across the test section was obtained with a differential pressure transducer. Data were obtained for several suspensions of Kraft pine pulps, a spruce pulp, and an eucalypt pulp, as well as for five polymer model fibres. Both the heat transfer and pressure drop data for the wood pulp fibre suspensions in general validated the results obtained from the pipeline investigations. The effect of fibre concentration on heat transfer coefficient hc and pressure drop ∆P/L are reported, and results are presented for the change in these variables with flow velocity over the range 0.1–2.0 m/s. There are some anomalous pressure drop ∆P/L data due to insufficient calming length and the additional exit and entrance losses. Both hc and ∆P/L values at 1.5 m/s and 0.4 percent fibre concentration are plotted against fibre length, fibre length-to-perimeter ratio, fibre stiffness, coarseness, and population. The data for the pine and spruce pulps were generally well correlated. Synthetic fibres with specific lengths, diameters, and modulus of elasticity values provide some further insights into the effects of key variables on hc and ∆P/L. It appears that fibre stiffness and fibre population are key variables but further tests are required with more synthetic fibres of different dimensions to validate the findings.