Pressure-sensitive paint measurement on co-rotating disks in a hard disk drive

There is much demand for improvement in the performance of a hard disk drive (HDD) along with recent rapid developments of information technology. While high-speed disk rotation of a HDD is necessary to accommodate such needs, it causes disk flutter induced by pressure fluctuation on disks and degrades reliability of a HDD. In order to understand the mechanism of the fluttering phenomenon, it is important to know pressure field on the rotating disk. However, it is impossible to measure the pressure by ordinary methods such as pressure taps. Pressure-sensitive paint (PSP) is a pressure measurement technique based on the oxygen quenching of luminescence and enables us to measure the pressure non-invasively. In general, however, the temperature sensitivity of PSP makes it difficult to measure the precise pressure on the surface with temperature distribution. We measured the time-averaged pressure on the disk rotating at 10 000-20 000 rpm for the first time by adopting a temperature-insensitive PSP composed of pyrene sulfonic acid (PySO₃H) as a luminophore. It was found that the pressure forms a concentric circular distribution and decreases toward the center of the disk. Additionally, we elucidate how disk rotational speed and spacing between co-rotating disks influence on the pressure field.     

Pressure sensitive paint evaluation on a supercritical wing at cruise speed

A comparative wind tunnel test of various Pressure Sensitive Paint (PSP) formulations has been performed at the Institute for Aerospace Research (IAR) 1.5 m×1.5 m Trisonic Blowdown Wind Tunnel. The model under study is a prototype supercritical wing of a half model. The results are presented at the cruise Mach number:M=0.74. The effect of the Reynolds number on the pressure distribution is assessed by varying the stagnation pressure of the flow. The evaluated paints all use the same porphyrin molecule as the luminescent sensor and the differences in sensitivity to pressure and temperature are a result of the PSP binder, which differs for each formulation. Examples of the processed results are given and the accuracy of the different PSP formulations is also discussed.     

Numerical simulation of the side pylon effect on the aerodynamic characteristics of models at their wind tunnel tests

The possible influence of fastening the models on a side pylon at their tests in wind tunnels on their aerodynamics at supersonic flow speeds has been considered. The physical problem of the pylon and the model interference has been investigated, and the estimates of the pylon influence on integral aerodynamic characteristics have been obtained. The numerical computations of the flow have been done using the averaged Navier-Stokes equations and the SST k-ω turbulence model in the range of freestream Mach numbers M = 2.5-5. As the investigation object the “classical” body of revolution of large aspect ratio is considered, which has a cruciform forward fins and six-blade tail stabilizers.     

Observations and simulations with linked numerical PBL and air pollution models and a Gaussian model under low wind speed conditions: a case study of the urban-industrial Linz area

Summary A one-week-long field study was carried out to investigate dispersion conditions and SO₂ patterns under low wind speed conditions in the industrial city of Linz. Meteorological fields generated with the URBMET PBL model were used as input for a 28 hour simulation of the SO₂ concentrations with a Eulerian model. Results were compared with the operational Gaussian model of the Austrian meteorological service. On the basis of balloon soundings at two sites, horizontal temperature profiles evaluated from car trips and the stationary observational network wind, temperature and SO₂ patterns were analysed and used to evaluate model results. Paper presented at the GNFAO/EURASAP Meeting, Turin, September 1989. To speed up publication, proofs were not sent to the authors and were supervised by the Scientific Committee.     

Characteristics of a hyperboloid-flare configuration at high Reynolds numbers

Results on a hyperboloid-flare model tested in a new hypersonic wind tunnel with adiabatic compression AT-303 based at ITAM SB RAS at M_∞ = 10 and 15 and in a wide range of Reynolds numbers are presented. Pressure and heat-flux distributions along the model are compared with data obtained previously in various European hypersonic wind tunnels (Longshot — Belgium, HEG — Germany) and with results of numerical computations. Pressure and heat-flux coefficients measured in the attached flow region are demonstrated to be in good qualitative agreement. Reasons for the differences in results measured in regions of flow separation and reattachment are discussed. Significant viscous effects on characteristics of the flow around the model are demonstrated; a particularly strong effect is exerted on the heat-flux distribution. This fact confirms that it is important to model real Reynolds numbers in wind-tunnel testing of aerospace plane models.     

Quantitative visualization of the leading-edge vortices on a delta wing by using pressure-sensitive paint

Leading-edge vortices on a simple delta wing were visualized by using pressure-sensitive paint (PSP). PSP is an optical pressure measurement technique based on oxygen quenching of luminescent molecules. In the present study, we used PSP composed of platinum octaethylporphyrine (PtOEP) and fluoropolymer (poly-IBM-co-TFEM [Poly (isobutylmethacrtlate-co-trifluoroethylate)]). This new paint has higher sensitivity to pressure and lower sensitivity to temperature than previous ones, reducing an error due to temperature variation during a wind tunnel test. A thin coating of PSP was applied to a delta wing model with 70-degree leading-edge sweep. The coating was excited by Xenon light and emission from the coating was detected by a high-resolution CCD camera. Tests were done at subsonic speeds in the 0.2-m Supersonic Wind Tunnel at the National Aerospace Laboratory in Japan. Complicated flow structures on the delta wing including primary and secondary vortices were clearly visualized using pressure-sensitive paint. An a priori calibration technique was used to convert measured luminescent intensity into pressure. The obtained pressure distributions were in good agreement with pressure tap data. Pressure maps were obtained for various Mach numbers, Reynolds numbers and angles of attack. It was found that an increase in Mach number delayed vortex breakdown while Reynolds number had little effect on the vortex formation.     

Convection driven zonal flows and vortices in the major planets

The dynamical properties of convection in rotating cylindrical annuli and spherical shells are reviewed. Simple theoretical models and experimental simulations of planetary convection through the use of the centrifugal force in the laboratory are emphasized. The model of columnar convection in a cylindrical annulus not only serves as a guide to the dynamical properties of convection in rotating sphere; it also is of interest as a basic physical system that exhibits several dynamical properties in their most simple form. The generation of zonal mean flows is discussed in some detail and examples of recent numerical computations are presented. The exploration of the parameter space for the annulus model is not yet complete and the theoretical exploration of convection in rotating spheres is still in the beginning phase. Quantitative comparisons with the observations of the dynamics of planetary atmospheres will have to await the consideration in the models of the effects of magnetic fields and the deviations from the Boussinesq approximation.     

Application of “POLIS” PIV system for measurement of velocity fields in a supersonic flow of the wind tunnels

Measurement results on the mean velocity fields and fields of velocity pulsations in the supersonic flows obtained by means of the PIV measurement set “POLIS” are presented. Experiments were carried out in the supersonic blow-down and stationary wind tunnels at the Mach numbers of 4.85 and 6. The method of flow velocity estimate in the test section of the blow-down wind tunnel was grounded by direct measurements of stagnation pressure in the setup settling chamber. The size of tracer particles introduced into the supersonic flow by a mist generator was determined; data on the structure of pulsating velocity in a track of an oblique-cut gas-dynamic whistle were obtained under the conditions of self-oscillations.     

Wind evaluation in the Adriatic sea

Summary A severe storm in the Adriatic Sea has been hindcast with two meteorological models, respectively at the local (LAMBO) and global scale (T213). We have found that the increase of resolution is not paralleled by a corresponding increase of the overall accuracy. This is particularly true when the wind fields are used to evaluate the corresponding wave fields. The LAMBO data have then been used to validate a simpler wind model that, when properly tuned to the specific basin and starting from the correct pressure fields, is capable to supply surface wind fields of acceptable quality. Deceased in November 1995.     

Preliminary application of a DGV system using a single intensified camera in a supersonic wind tunnel

A DGV system using a continuous wave Argon laser and an optical arrangement with a single intensified camera has been set up at the ISL blow-down supersonic wind tunnel. The first tests have been performed over a 12.5° 2D wedge at a freestream Mach number of 2. A mean velocity field has been calculated from 28 individual measurements. When compared to the theoretical velocity distribution, deviations of 8 % to 15 % have been obtained. Preliminary tests have also been performed on a missile-like model equipped with a lateral jet system. Individual as well as mean velocity fields are presented.     

Characteristics of the AT-303 hypersonic wind tunnel. Part 1. Velocity Fields

The structure and principle of operation of a new wind tunnel AT-303 with adiabatic compression are described. Results of systematic investigations are presented in terms of velocity distributions both at the nozzle exit and in the region where the models are located. The velocity fields are obtained with the use of total pressure probes in the ranges of Mach numbers from 7.6 to 19.7 and Reynolds numbers per meter Re₁ = (0.25−3.64)·10⁷.     

Characteristics of the AT-303 hypersonic wind tunnel. Part 2. Aerodynamics of the HB-2 reference model

Aerodynamic coefficients of the HB-2 AGARD reference model measured in a new AT-303 hypersonic wind tunnel with adiabatic compression are presented. The experiments are performed in the ranges of Mach numbers M = 9.7 − 15.6 (Re_d = 0.14·10⁶ − 1.32·10⁶) and angles of attack α = −4°−12° with the use of an internal six-component strain-gauge balance. The technique used for processing and correcting measured results, which takes into account the dynamic properties of the model and the specific features of the nozzle structure, is described in detail. The aerodynamic coefficients obtained for this model are compared with similar data obtained in wind tunnels of Germany, France, and the USA.     

旋转状态下篦齿-蜂窝结构封严特性研究

本文对篦齿-蜂窝封严结构的封严特性进行了三维数值仿真,研究了不同结构参数、旋转速度及气动参数对其封严特性的影响,并与篦齿-涂层封严结构进行了对比.结果表明:采用蜂窝结构能改变篦齿腔内气体的流动,有效降低泄漏;篦齿前后腔气动参数一定时,齿数增加、篦齿节流间隙宽度减小或转速增加,泄漏量和泄漏系数都会相应减少.     

Automotive testing using pressure-sensitive paint

Measurements of the surface pressure on a simplified automobile model have been performed using pressure-sensitive paint (PSP). The program was undertaken to investigate the use of commercial and in-house PSP at low speed (between 11 m/s and 92 m/s) and to find techniques to improve the measurement accuracy. A comparison ofa priori andin situ calibration methods was also conducted. A linearin situ calibration ora priori methods combined with one tap pressure, correcting for bias errors, were found to provide the best accuracy.     

Visualization of aerodynamic effects on a double-delta wing aircraft model using Pressure Sensitive Paint (PSP) technique

Visualization of aerodynamic effects on a three-dimensional double-delta wing aircraft model was conducted using an optical pressure measurement system, based on the Pressure Sensitive Paint (PSP) technique, and in addition a laser-light sheet method. The combination of PSP technology with the laser-light sheet method, provides a good understanding of the flow around the wind tunnel model. In recent years, this novel PSP-technology has attracted considerable attention in the aerospace community. The PSP technique can be used to realize absolute pressure measurements on a surface of a model and in addition to evaluate quantitative aerodynamic flow phenomena using a scientific grade camera and image processing techniques. The PSP system was tested in the Transonic Wind Tunnel of the German Aerospace Center in Göttingen (TWG) under real flow conditions. Instantaneous pressure distributions are recorded in almost real-time so that the recognition and analysis of the vortex dynamics on the model surface is possible. Even the vortex breakdown process, as well as the fine structured Kelvin-Helmholtz instabilities and secondary vortex structures, can be detected by this measurement technique.     

PSP visualization studies on a convergent nozzle with an

An in-house Pressure Sensitive Paint (PSP) formulation has been developed at the Aero-Physics Laboratory at the University of Manchester. The PSP uses Bathophenanthroline Ruthenium as the luminophore molecule and is incorporated in a sol-gel matrix. Excitation occurs at400–500 nm and emission at550–650 nm. The Stern-Volmer plot of the PSP reveals small temperature dependence, which has always been an intrinsic drawback of PSPs. As a baseline experiment the PSP has been applied to examine the side-wall pressure field of the flow through a convergent nozzle with an ejector, at fully expanded Mach numbers in the rangeM _j =0.52–1.36. Simultaneous static pressure measurements were also conducted to ascertain the accuracy of the PSP results. The paint has demonstrated satisfactory capabilities in not only measuring static pressures but also in visualizing key physical elements of the flow, such as the location of the expansion and oblique shock waves present in such flows.     

Assisted Inflation in Bianchi VI0 Cosmologies

Exact models for Bianchi VI₀ spacetimes with multiple scalar fields with exponential potentials have been derived and analysed. It has been shown that these solutions, when they exist, attract neighbouring solutions in the two cases corresponding to interacting and non-interacting fields. Unlike the results obtained in a previous work dealing with the late-time inflationary behaviour of Bianchi VI₀ cosmologies, the knowledge of exact solutions has made possible to study in detail the occurrence of inflation before the asymptotic regime. As happened in preceding works, here as well inflation is more likely to happen with a higher number of non-interacting fields or a lower number of interacting scalar fields.     

A magnetically stabilized coaxial laser discharge

A new magnetic discharge stabilization technique for coaxial laser systems is described. The approach utilizes crosses electric and magnetic fields to create and maintain a large and rapidly rotating plasma volume which does not experience glow-to-arc transitions. Very high cw specific discharge power loadings have been achieved even without the benefit of external gas cooling or circulation.Performance is insensitive to gas composition and pressure such that high power coaxial discharges have been run in CO₂ laser gas mixtures up to several hundred torr. Stable cw discharges have also been obtained in mixtures containing several torr of SF₆.The technique appears to be readily scalable to give very large excited volumes in systems with comparatively small overall physical dimensions.     

Visualization of transient three-dimensional flow field with rotating stall in a diagonal flow fan

An Unsteady flow field with rotating stall cells in a high specific-speed diagonal flow fan has been investigated experimentally. Although a general feature of stall cells has already indicated, i.e., the number of stall cells is one and its propagating speed is approximately 80 percent of rotor speed, little has been known about the flow field when a rotating stall occurs because of its unsteadiness. In order to capture the behavior of the rotating stall cell, measurements of the flow field at the rotor inlet were carried out with a single slant hot-wire. Those data were processed by a so-called “double phase-locked averaging” (DPLA) technique, which enabled to capture the flow field of the cell in the reference co-ordinate system fixed to the rotor. As a result, time-dependent ensemble averages of the three-dimensional velocity components at the rotor inlet have been obtained and the behavior of the rotating stall cell has been illustrated with each velocity component.     

Precision improvements in the geo-fit retrieval of pressure and temperature from MIPAS limb observations by modeling CO2 line-mixing

In this paper, we present an improvement of the retrieval of pressure and temperature from the observations of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board of the environmental satellite (ENVISAT). The improvement has been obtained by integrating a state-of-the-art CO₂ line-mixing model in a two-dimensional inversion system (Geo-fit). We describe the implementation of this model in the Geo-fit system and we show its capability to reproduce the CO₂ spectral features affected by line-mixing. The upgraded analysis algorithm provides a better fit of the set of MIPAS observations analyzed by the European Space Agency (ESA) ground segment although these observations have been selected with criteria that should avoid line-mixing effects. Moreover, we show that this set of observations can be extended improving the precision of the retrieved pressure and temperature fields without increasing the computing demands. Since the CO₂Q branches are very sensitive to pressure and temperature, the capability to model accurately the line-mixing effects opens the possibility to exploit at best these spectral regions to infer pressure and temperature distributions. According to this idea, we propose a new set of spectral intervals, including the most intense CO₂Q branches. It is shown that the analysis of these intervals provides a significant improvement (up to 70%) in the precision of the retrieved pressure and temperature profiles, while using a smaller number of observations with respect to the ESA ground segment analysis. Since the knowledge of pressure and temperature is necessary for the retrieval of the altitude distribution of all the atmospheric constituents, the benefits of more precise pressure and temperature fields obtained in this work propagate into the quality of all the MIPAS products.