Disk Pump Research Articles

Laboratory experiments on turbulent mixing across sheared density interfaces

An experimental study was carried out to investigate turbulent mixing and entrainment across a density interface subjected to velocity shear. The flow configuration consisted of a salinity (stably) stratified two-fluid system with a driven upper turbulent layer and a quiescent lower layer. The experiments were performed in an Odell–Kovasznay tank and the mean flow in the upper layer was generated by using a conventional disk pump. The velocity and salinity measurements were made using a laser-Doppler anemometer and conductivity probes, respectively, and (quantitative) flow visualization was performed using the laser-induced fluorescence LIF technique. The refractive indices of upper and lower layers were matched, using salt and alcohol, to facilitate the use of laser-based flow diagnostic techniques. The measurements show that the rms velocity fluctuation u in bulk of the mixed layer scales well with the mean velocity jump Δu across the interface. The Thorpe, buoyancy, overturning, and integral length scales, as well as the maximum Thorpe displacement in the mixed layer, were also found to be proportional to the depth h of the upper mixed layer. The structure of the entrainment interface was found to depend strongly on the bulk Richardson number Ri (=Δb h/u2), where Δb is the buoyancy jump across the interfacial layer. At lower Ri, the entrainment occurred rapidly, as in a nonstratified fluid, but as Ri increases, the entrainment rate becomes a strong function of Ri: under the latter conditions, the interfacial wave breaking and Kelvin–Helmholtz instabilities were common features. At still higher Ri, the entrainment rate becomes vanishingly small and the interfacial mixing events were found to be controlled by the molecular diffusive effects. The measurement of the interfacial-layer thickness using LIF shows that it is much thinner than that measured using less-accurate techniques such as traversing probes. The nondimensional rms amplitude of the interfacial distortions at moderate and high Ri was found to be a strong function of Ri. The interfacial instabilities cause the formation of isolated mixing patches within the interface, which, when collapsed, form horizontal intrusions. The experimental measurements were in agreement with theoretical formulations based on scaling arguments.

The Optimum Groove Geometry for Spiral Groove Viscous Pumps

The optimum geometries of disk and cylindrical sprial groove viscous pumps to provide the maximum pressure or flow rate are investigated theoretically. The geometrical design parameters, such as the groove angle, groove to ridge clearance ratio, groove width ratio and ridge clearance ratio, are considered as functions of meridional coordinate. Results are obtained from the solution of a differential equation for the smoothed overall pressure distribution of a spiral groove viscous pump. It is found that outflow rate increases with the increase of groove to ridge clearance ratio λ, and that for each value of λ there exist “optimum” values of groove angle and groove width ratio, which give a maximum outflow rate. However, the increase of λ decreases the ridge clearance.

Growth of GaAs in a rotating disk MOCVD reactor

We report the growth of GaAs homoepitaxial films from trimethylgallium and arsine in a multi-wafer rotating disk reactor. In this configuration the substrates are mounted on a disk that is spun at high speed (> 1000 rpm) in a sub-atmospheric (<100 Torr) environment. The spinning disk pumps the reactant and carrier gases radially outwards; under optimum conditions, convective recirculating cells are avoided, thus facilitating rapid transitions in doping and composition in the grown layers. In this paper we look at the morphology, growth rate and electrical properties of the GaAs epitaxial layers as a function of substrate temperature, V/III ratio, dopant type, spin speed and hydrogen carrier flow conditions. These results are compared with those obtained in conventional MOCVD reactors. Silicon and tellurium doping over a wide range of carrier concentrations has been achieved with excellent mobilities and uniformity across the wafers. Preliminary results on MESFET's fabricated from n +/n/buffer structures show good device characteristics.

On the sheared density interface of an entraining stratified fluid

This paper deals with the nature of the entrainment interface of a two-layer fluid subjected to interfacial velocity shear. The shear flow was generated by driving the mixed layer over the dense layer by a disk pump such that there is no stress at the top of the mixed layer. During the entrainment process a sharp, thin-density interfacial layer developed; its thickness δ was found to increase linearly with the mixed-layer depth h, independent of the Richardson number Riu. The shear layer thickness δs was found to be much larger than δ and the ratio δs/h is also found to be constant, irrespective of Riu. At the entrainment interface, the estimated buoyancy flux and the dissipation of turbulent kinetic-energy appear to be of the same order. This result supports an entrainment law of the form E ∼ Riu−1, where E is the entrainment coefficient. The interfacial layer showed sporadic large-amplitude wave oscillations whose amplitudes scaled well with the estimated size of the undulations caused by the impingement of large eddies (of size h) on the density interface. The density-interfacial layer was found to be ‘topped’ by a layer of partially mixed fluid which had not yet incroporated into the well-mixed region.

Effects of Honeycomb-Shaped Walls on the Flow Regime Between a Rotating Disk and a Stationary Wall

In gas turbines there are many circumstances where coolant flows are introduced between the rotor disk and the stationary housing. This flow serves not only to supply coolant flow to the disk face, but also to restrict the radial inflow of hot gases to be ingested into the clearance from the turbine blade flow field. The amount of the hot radial inflow is influenced by the difference of the disk pumping capacity and the coolant flow supplied near the center. In order to cool the turbine disk with limited supply of coolant air, some means of reducing the radial inflow of hot gases is needed. It is thought that the use of different surface shapes on the stationary housing would inhibit the disk pumping capacity and, therefore, reduce the radial inflow of hot gases into the clearance. To validate the concept, an experimental study was undertaken. The basic geometry investigated was the flow field between a smooth cylindrical rotating disk parallel to a plain circular coaxial wall open to the free space at the disk periphery. Coolant flow is simulated by supplying air through the bore of the stationary wall into the gap. In addition to the base data obtained with the plain stationary wall, a duplicate series of experiments were run with an open honeycomb facing the stationary wall. The effects of the stationary wall surface geometry is assessed by comparing the data with honeycomb facing against the data with plain stationary wall. The flow field is studied through measurements of the static pressure on the stationary wall, radial and tangential velocity measurements in the clearance, the torque on the drive motor, and coolant flow rates. Flows were studied over a gap spacing to disk radii ratio of 0.01 and 0.10, disk Reynolds numbers from 5×105 to 2.2×106, and throughflow rates from 0 to 3.2 cfs. The results are presented in terms of the tangential and radial velocity profiles in the gap, the static pressure measurements, and the disk torque coefficients. The use of honeycomb on the stationary wall surface grossly altered the ingestion of external flow into the gap from the disk periphery. Important conclusions are: (1) The vacuum in the gap generated by the disk rotation is reduced by a factor of 0.4 to 0.6, depending on the radial location of the point; (2) the core tangential velocity is reduced by a factor of 0.6 to 0.7, depending on the axial spacing and the throughflow number; (3) the critical coolant flow rate is about 63 percent less for the honeycombed surface, as compared to the plain wall case. (4) for a given coolant flow rate, the penetration distance of the radial inflow is much larger for the plain disk than the honeycomb surface.

Entrainment due to turbulent shear flow at the interface of a stably stratified fluid

An investigation is made of the entrainment due to turbulent shear flow at the interface of a stably stratified fluid between an upper turbulent layer and a lower non-turbulent layer in which the flow is generated by a disc pump in a recirculating channel, first introduced by Odell and Kovasznay. It is found that, based on friction velocity u * and on mean velocity U , the plots of the entrainment rates as functions of the corresponding Richardson numbers for two-fluid systems and for linearly stratified systems are in agreement and collapse, so that the two systems follow the same entrainment law. The entrainment rates of the present investigation agree with those of Kantha et al., and for the most part with entrainment rates of Kranenburg. The entrainment rates of Moore and Long are also in agreement with those of present study, as are the heat-stratified entrainment rates of Deardorff and Willis. Using δ b for the buoyancy jump and h for mixed-layer depth, limiting values of Ri* = hδb / u 2 * ≅ 2000 and Ri u = hδb / U 2 ≅ 20 are obtained experimentally as E* = u e / u e and E u = u e / U approach zero and turbulent entrainment ceases, in agreement with an argument of Kantha. Also, limiting values of E * ≃ 0.3 and E u ≃ 0.03, are found for small values of Ri*, based on an argument of Tennekes and Lumley. Although no simple power-law dependence of entrainment rates on Richardson number is obtained for the whole range of Ri*, it was possible to obtain such dependence when the range 15 < Ri* < 1500 is divided into 3 smaller subranges. DOI: 10.1111/j.1600-0870.1986.tb00454.x

Corotating disk pumps for viscous liquids

Corotating disk pumps for viscous liquids

Isothermal flow of a non-Newtonian fluid through the channel of a volute-type disk pump under conditions of complex shear

A study is made pertaining to steady laminar flow of an anomalously viscous fluid between two rigid disks in one of which the thread has been cut in the form of an Archimedes spiral.

Jet Cooling at the Rim of a Rotating Disk

Results are presented from an experimental study conducted to measure heat transfer rates at the rim of a rotating disk convectively cooled by impinging jets. The disk face contour radially inward from the rim is varied to simulate the geometric conditions found on gas turbine engine rotors. Heat transfer rates are found to be relatively unaffected by impingement for jet flowrates less than the order of one-tenth the disk pumping flow. Disk pumping flows are evaluated through the use of an analysis which accounts for the presence of the disk hub. At larger jet flowrates, heat transfer rates increase strongly with increasing jet flow, reaching two to three times the no-impingement values at jet flowrates approximately equal to the pumped flow. All the heat transfer results, both with and without jet impingement, are essentially unaffected by changes in the disk face contour.

Accretion disk coronae and Cygnus X-1

view Abstract Citations (195) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Accretion disk coronae and Cygnus X-1. Liang, E. P. T. ; Price, R. H. Abstract It is plausible that an accretion disk pumps energy into an outer tenuous layer of its atmosphere to form a high-temperature corona analogous to the solar corona. General features of such a corona, not specific to any model, are discussed, and order-of-magnitude estimates are made for the physical parameters of a corona on the Cygnus X-1 disk. It is shown that a corona with a strong 'wind' (mass loss flux) can produce hard (exceeding 100 keV) X-rays if it is cooled by inverse Compton scattering. An observational test for the presence of such a corona is suggested. Publication: The Astrophysical Journal Pub Date: November 1977 DOI: 10.1086/155677 Bibcode: 1977ApJ...218..247L Keywords: Binary Stars; Stellar Atmospheres; Stellar Mass Accretion; Stellar Winds; X Ray Stars; Energy Levels; Solar Corona; Stellar Mass Ejection; Stellar Models; Stellar Radiation; Astrophysics full text sources ADS | data products SIMBAD (1)

Heat Transfer Between an Impinging Jet and a Rotating Disk

An experimental study of the flow interaction and heat transfer between a single impinging jet and a rotating disk is presented. Tests were conducted over a range of jet flowrates, impingement radii, and disk rotational speeds with various combinations of three jet and three disk sizes. Flow visualization using smoke addition to the jet flow reveals the presence of a flow regime transition which is correlated in terms of the rotationally induced disk pumping flow acting as a cross-flow influence on the jet. Higher rotational speeds, larger impingement radii, and smaller jet flowrates favor a rotationally dominated flow interaction whereas the opposite trends favor an impingement dominated interaction. Heat transfer rates are essentially independent of jet flowrate in the rotationally dominated regime, but increase, strongly with increasing flowrate in the impingement dominated regime.

Investigations on the Pumping Effect of Rotating Discs

The mathematical and experimental work described in this paper were carried out in the pump laboratory of the Rocket Propulsion Establishment (RPE) Westcott in 1955. In 1956 test runs took place with a ‘disc pump’ the impeller of which was described in the author's paper (l)t (Figs 19, 20 and 21)† The information in the present paper was not made widely available by the RPE, at that time. Since the author's view the treatment used differs widely from that described in later publications (see References in Appendix 3); the results can be readily applied to practical design work.

Flow Regime Definition for Flow Between Corotating Disks

Experimental data and results are presented for the flow of an incompressible Newtonian fluid, with full admission, between closely spaced corotating disks, and for both radially inward and radially outward throughflows. The data consist of the measured radial pressure distribution together with flow visualization by means of injected dye, over a very wide range of parameters descriptive of the flows. From the data, the combinations of the parameters corresponding with laminar and with turbulent flow are determined; that is, the data are sufficient to define the flow regimes. Furthermore, for laminar flow, both the pressure distribution data and the flow visualization data confirm the adequacy of earlier analytical results for use in the design of practical devices incorporating these flows, such as multiple disk pumps and turbines.

A new type of water channel with density stratification

The novel idea is to use a disk pump to drive each fluid layer independently round a closed-return density-stratified water channel. A small-scale model was built and tested to demonstrate the feasibility of the idea. A hydrogen-bubble technique was used for both flow visualization and velocity measurement. Density measurements were made with an electrical conductivity probe developed by the authors. The tests have demonstrated the usefulness of such a facility, especially for long steady-state experiments in density-stratified flows.

Heat Transfer and Pumping on a Rotating Disk With Freely Induced and Forced Cooling

An experimental study of the heat transfer characteristics of flows between a high speed rotating disk and a parallel stationary shroud is presented. Flow and disk heat transfer rates have been determined for various combinations and rates of freely induced and forced flows supplied at both the hub and rim of the disk. The study models a practically important class of turbine rotor cooling problems where small flow rates similar in magnitude to the disk pumping flows are of interest. The experimental facility and procedures are described in detail. They have been designed to facilitate rapid and economical acquisition of rotor cooling characteristics in situations where the particular rotor-shroud geometry makes existing correlations inadequate.

Influence of a defoaming agent upon the hematological complications of pump oxygenators.

Measurements of plasma hemoglobin values were made at many different sites of a Cross-Kay disk pump oxygenator during extracorporeal bypass in patients undergoing reparative valve surgery. Hemoglobin values were always higher in the line of the aspirator and defoaming chamber than in any other part of the system. Sampling immediately proximal and distal to the defoaming chamber revealed significant increases in plasma hemoglobin values as a result of the defoaming process. Studies of the hematological effects of the defoaming agent, polymethylsiloxane, which coats the disposable stainless steel sponge in the defoaming chamber, showed it greatly reduced the resistance of red cells to lysis by mechanical trauma. Similar studies of plasma showed the hemolytic effects of the defoaming agent are to some extent mediated by the plasma. It is concluded that the widely used defoaming agent, polymethylsiloxane, contributes to the hemolytic action of the bubbling, suctioning, and defoaming processes during open heart surgery. The addition of a water soluble surfactant material, that stabilizes emulsions (Pluronic F68), blocked or prevented the hemolytic process without interfering with the action of the antifoam material.

Closure to “Discussions of ‘An Analytical and Experimental Investigation of Multiple Disk Pumps and Compressors’” (1963, ASME J. Eng. Power, 85, pp. 199–200)

Closure to “Discussions of ‘An Analytical and Experimental Investigation of Multiple Disk Pumps and Compressors’” (1963, ASME J. Eng. Power, 85, pp. 199–200)

Discussion: “An Analytical and Experimental Investigation of Multiple Disk Pumps and Compressors” (Rice, Warren, 1963, ASME J. Eng. Power, 85, pp. 191–198)

Discussion: “An Analytical and Experimental Investigation of Multiple Disk Pumps and Compressors” (Rice, Warren, 1963, ASME J. Eng. Power, 85, pp. 191–198)

Discussion: “An Analytical and Experimental Investigation of Multiple Disk Pumps and Compressors” (Rice, Warren, 1963, ASME J. Eng. Power, 85, pp. 191–198)

Discussion: “An Analytical and Experimental Investigation of Multiple Disk Pumps and Compressors” (Rice, Warren, 1963, ASME J. Eng. Power, 85, pp. 191–198)

An Analytical and Experimental Investigation of Multiple Disk Pumps and Compressors

An unconventional type of turbomachinery employing a rotor composed of smooth disks is described and the history and motive principle of such devices briefly recounted. An experimental program of research on such devices is described, together with a description of the design and testing of an experimental water pump, a blower, and an air compressor using multiple disk rotors. Data resulting from the testing of the devices are presented in summary form with discussions of the conclusions which the data allow. A “first-approximation” analysis is presented of the flow processes within the rotor and of the limiting performance and efficiency of multiple disk pumps. Solution of the resulting equations, found by digital computation, is presented for a wide range of geometry and of flow variables, in terms of dimensionless parameters. A brief discussion is given of possible applications of multiple dish pumps, compressors and blowers, and of the information now available for the design of the devices.