Showing papers by "Steven L. Ceccio published in 2009"

Growth, oscillation and collapse of vortex cavitation bubbles

Abstract: The growth, oscillation and collapse of vortex cavitation bubbles are examined using both two- and three-dimensional numerical models. As the bubble changes volume within the core of the vortex, the vorticity distribution of the surrounding flow is modified, which then changes the pressures at the bubble interface. This interaction can be complex. In the case of cylindrical cavitation bubbles, the bubble radius will oscillate as the bubble grows or collapses. The period of this oscillation is of the order of the vortex time scale, τV = 2πrc/uθ, max, where rc is the vortex core radius and uθ, max is its maximum tangential velocity. However, the period, oscillation amplitude and final bubble radius are sensitive to variations in the vortex properties and the rate and magnitude of the pressure reduction or increase. The growth and collapse of three-dimensional bubbles are reminiscent of the two-dimensional bubble dynamics. But, the axial and radial growth of the vortex bubbles are often strongly coupled, especially near the axial extents of the bubble. As an initially spherical nucleus grows into an elongated bubble, it may take on complex shapes and have volume oscillations that also scale with τV. Axial flow produced at the ends of the bubble can produce local pinching and fission of the elongated bubble. Again, small changes in flow parameters can result in substantial changes to the detailed volume history of the bubbles.

High-Reynolds-number turbulent boundary layer friction drag reduction from wall-injected polymer solutions

Abstract: ALMEIDA TG, 2006, P 26 S NAV HYDR ROM; Bailey F., 1959, J APPL POLYM SCI, V1, P56, DOI 10.1002-app.1959.070010110; BATCHELOR GK, 1957, J FLUID MECH, V3, P67, DOI 10.1017-S0022112057000488; Beris AN, 1999, COMPUT METHOD APPL M, V180, P365, DOI 10.1016-S0045-7825(99)00174-7; BRUNGART TA, 1991, EXP FLUIDS, V11, P9, DOI 10.1007-BF00198427; COX LR, 1974, NATURE, V249, P243, DOI 10.1038-249243a0; Dealy JM, 2006, STRUCTURE RHEOLOGY M; Dubief Y, 2004, J FLUID MECH, V514, P271, DOI 10.1017-S0022112004000291; DUNLOP EH, 1977, PHYS FLUIDS, V20, pS203, DOI 10.1063-1.861731; Etter RJ, 2005, MEAS SCI TECHNOL, V16, P1701, DOI 10.1088-0957-0233-16-9-001; Faraone A, 1999, J CHEM PHYS, V110, P1801, DOI 10.1063-1.477888; FONTAINE AA, 1992, J FLUID MECH, V238, P435, DOI 10.1017-S0022112092001770; Fruman D.H., 1976, J SHIP RES, V20, P171; Ho DL, 2003, J POLYM SCI POL PHYS, V41, P135, DOI 10.1002-polb.10340; HORN AF, 1984, NATURE, V312, P140, DOI 10.1038-312140a0; Housiadas KD, 2003, PHYS FLUIDS, V15, P2369, DOI 10.1063-1.1589484; Jimenez J, 1999, J FLUID MECH, V389, P335, DOI 10.1017-S0022112099005066; Kalashnikov VN, 1998, J NON-NEWTON FLUID, V75, P209, DOI 10.1016-S0377-0257(97)00093-1; KALASHNIKOV VN, 1994, J RHEOL, V38, P1385, DOI 10.1122-1.550550; LOTTO B, 1981, J RHEOL, V25, P583; PATEL VC, 1965, J FLUID MECH, V23, P185, DOI 10.1017-S0022112065001301; PETRIE H, 1996, ASME FED, V237, P3; Petrie HL, 2005, P 2 INT S SEAW DRAG, P605; Petrie HL, 2003, EXP FLUIDS, V35, P8, DOI [10.1007-S00348-003-0589-X, 10.1007-s00348-003-0589-x]; PETRIE HL, 1996, P ASME FLUIDS ENG DI, V237, P205; Polverari M, 1996, J PHYS CHEM-US, V100, P13687, DOI 10.1021-jp960215o; Poreh M., 1972, Journal of Hydronautics, V6, DOI 10.2514-3.48119; Poreh M., 1964, International Journal of Heat and Mass Transfer, V7, DOI 10.1016-0017-9310(64)90032-8; Ptasinski PK, 2003, J FLUID MECH, V490, P251, DOI 10.1017-S0022112003005305; Sanders WC, 2006, J FLUID MECH, V552, P353, DOI 10.1017-S0022112006008688; Schultz-Grunow F., 1941, NACA T M, V17, P1; Sellin R.H., 1982, J HYDRAUL RES, V20, P29; SOMMER ST, 1992, EXP FLUIDS, V12, P181; Tirtaatmadja V, 2006, PHYS FLUIDS, V18, DOI 10.1063-1.2190469; VANAPALLI SA, 2005, PHYS FLUIDS, V17, P1; Vanapalli SA, 2006, P NATL ACAD SCI USA, V103, P16660, DOI 10.1073-pnas.0607933103; VANAPALLI SA, 2007, THESIS U MICHIGAN; VDOVIN AV, 1978, J APPL MECH TECH PHY, V19, P66; VDOVIN AV, 1981, J APPL MECH TECH PHY, V22, P98; VIRK PS, 1970, J APPL MECH, V37, P488; VIRK PS, 1967, J FLUID MECH, V30, P305, DOI 10.1017-S0022112067001442; VIRK PS, 1975, AICHE J, V21, P625, DOI 10.1002-aic.690210402; Vlachogiannis M, 2004, EXP FLUIDS, V36, P685, DOI 10.1007-s00348-003-0745-3; VLASSOPOULOS D, 1994, J RHEOL, V38, P1427, DOI 10.1122-1.550605; WALKER DT, 1986, EXP FLUIDS, V4, P114, DOI 10.1007-BF00266568; Warholic MD, 1999, EXP FLUIDS, V27, P461, DOI 10.1007-s003480050371; White CM, 2004, EXP FLUIDS, V36, P62, DOI 10.1007-S00348-003-0630-0; WHITE F. M., 2005, VISCOUS FLUID FLOW; Winkel E. S., 2006, P 26 S NAV HYDR ROM; WU J, 1972, T ASME, V94, P749

Experimental mistuning identification in bladed disks using a component-mode-based reduced-order model

Abstract: smallsetofmeasuredbladevibrationamplitudesintocoordinatesinahighlyreduced-ordermodelinwhichtheblade modal stiffnesses appear explicitly. The effectiveness of both methods is demonstrated experimentally.

Degradation of homogeneous polymer solutions in high shear turbulent pipe flow

Abstract: This study quantifies degradation of polyethylene oxide (PEO) and polyacrylamide (PAM) polymer solutions in large diameter (2.72 cm) turbulent pipe flow at Reynolds numbers to 3 × 105 and shear rates greater than 105 1/s. The present results support a universal scaling law for polymer chain scission reported by Vanapalli et al. (2006) that predicts the maximum chain drag force to be proportional to Re 3/2, validating this scaling law at higher Reynolds numbers than prior studies. Use of this scaling gives estimated backbone bond strengths from PEO and PAM of 3.2 and 3.8 nN, respectively. Additionally, with the use of synthetic seawater as a solvent the onset of drag reduction occurred at higher shear rates relative to the pure water solvent solutions, but had little influence on the extent of degradation at higher shear rates. These results are significant for large diameter pipe flow applications that use polymers to reduce drag.

Testing and Calibration Procedures for Mistuning Identification and Traveling Wave Excitation of Blisks

Abstract: In this work, an integrated testing and calibration procedure is presented for performing mistuning identification (ID) and traveling wave excitation (TWE) of one-piece bladed disks (blisks). The procedure yields accurate results while also being highly efficient and is comprised of three basic phases. First, selected modes from a tuned blisk finite element model are used to determine a minimal set of measurement degrees of freedom (and locations) that will work well for mistuning ID. Second, a testing procedure is presented that allows the mistuning to be identified from relatively few vibration response measurements. A numerical validation is used to investigate the convergence of the mistuning ID results to a prescribed mistuning pattern using the proposed approach and alternative testing strategies. Third, a method is derived to iteratively calibrate the excitation applied to each blade so that differences among the blade excitation magnitudes can be minimized for single blade excitation, and also the excitation phases can be accurately set to achieve the desired traveling wave excitation. The calibration algorithm uses the principle of reciprocity and involves solving a least squares problem to reduce the effects of measurement noise and uncertainty. Because the TWE calibration procedure re-uses data collected during the mistuning ID, the overall procedure is integrated and efficient.Copyright © 2009 by ASME

Temporal evolution of flame stretch due to turbulence and the hydrodynamic instability

Abstract: The temporal evolution of the strain rate on a turbulent premixed flame was measured experimentally using cinema-stereoscopic particle image velocimetry. Turbulence strains a flame due to velocity gradients associated both directly with the turbulence and those caused by the hydrodynamic instability, which are initiated by the turbulence. The development of flame wrinkles caused by both of these mechanisms was observed. Wrinkles generated by the turbulence formed around vortical structures, which passed through the flame and were attenuated. After the turbulent structures had passed, the hydrodynamic instability flow pattern developed and caused additional strain. The hydrodynamic instability also caused the growth of small flame front perturbations into large wrinkles. In the moderately turbulent flame investigated, it was found that the evolution of the strain rate caused by turbulence–flame interactions followed a common pattern involving three temporal regimes. In the first, the turbulence exerted extensive (positive) strain on the flame, creating a wrinkle that had negative curvature (concave towards the reactants). This was followed by a transition period, leading into the third regime in which the flow pattern and strain rate were dominated by the hydrodynamic instability mechanism. It was also found that the magnitudes of the strain rate in the first and third regimes were similar. Hence, the hydrodynamic instability mechanism caused significant strain on a flame and should be included in turbulent combustion models.

Three-dimensional temporally resolved measurements of turbulence–flame interactions using orthogonal-plane cinema-stereoscopic PIV

Abstract: A new orthogonal-plane cinema-stereoscopic particle image velocimetry (OPCS-PIV) diagnostic has been used to measure the dynamics of three-dimensional turbulence–flame interactions. The diagnostic employed two orthogonal PIV planes, with one aligned perpendicular and one aligned parallel to the streamwise flow direction. In the plane normal to the flow, temporally resolved slices of the nine-component velocity gradient tensor were determined using Taylor’s hypothesis. Volumetric reconstruction of the 3D turbulence was performed using these slices. The PIV plane parallel to the streamwise flow direction was then used to measure the evolution of the turbulence; the path and strength of 3D turbulent structures as they interacted with the flame were determined from their image in this second plane. Structures of both vorticity and strain-rate magnitude were extracted from the flow. The geometry of these structures agreed well with predictions from direct numerical simulations. The interaction of turbulent structures with the flame also was observed. In three dimensions, these interactions had complex geometries that could not be reflected in either planar measurements or simple flame–vortex configurations.

Bragg cell laser intensity modulation: effect on laser Doppler velocimetry measurements.

Abstract: In most laser Doppler velocimetry (LDV) systems, the frequency of one of the two laser beams that intersect to create the probe volume is shifted with an acousto-optic element. It is shown here that Bragg shifting can impose a problematic fluctuation in intensity on the frequency-shifted beam, producing spurious velocity measurements. This fluctuation occurs at twice the Bragg cell frequency, and its relative amplitude to the time average intensity is a function of the ratio of the laser beam diameter to the Bragg cell acoustic wavelength. A physical model and a configuration procedure to minimize adverse effects of the intensity modulations are presented.

Mechanism and scalability of tip vortex cavitation suppression by water and polymer injection

Abstract: Tip Vortex Cavitation (TVC) suppression via mass injection in the core of the vortex was studied with an elliptical plan-form hydrofoil NACA-66 modified in a re-circulating water tunnel with known nuclei distribution. The chord base Reynolds number was O(10 6 ) for all the experiments. The injectants were water and Polyox WSR-301 solutions with concentration ranging from 10 to 500 wppm. Flow rates of 0.033 < Qjet / Qcore < 0.27 were examined. It was found that the TVC suppression effect was more pronounced for inception than for desinence. For inception, a suppression effect was observed for all cases of mass injection. The baseline inception cavitation number, σΙ = 3.3, was higher than the average minimum pressure coefficient, -Cp = 2.3 inferred from the average vortex flow properties near the location of TVC inception. Injection of mass into the core reduced the observed inception cavitation number to a value that was consistent with the average value such that σΙ ∼ σD ~ –Cp. The measured TVC desinence value for the baseline case was found to match the expected minimum –Cp. The effect on polymer injection on TVC desinence was twice as strong as that for water injection. The mechanisms that lead to TVC suppression via mass injection are also discussed. INTRODUCTION Tip vortex cavitation (TVC) the inception and development that is associated with lifting surface has been extensively studied due to their importance in the design of turbomachinery and propulsors (Arndt, 2002). The flow fields and resulting TVC has been studied on elliptic planform hydrofoils by numerous researchers, including Fruman et al. (1991), Fruman et al. (1992), and Arndt and Maines (1994) and (2000). These studies reveled the importance of both the detailed flow around the hydrofoil tip and the ambient nuclei distribution to the process of TCV inception. A number of methods have been developed to delay the onset of TVC. The strategies used can be classified into passive and active methods. A survey of several different strategies is presented by Platzer and Souders (1979). Examples of passive methods are hydrofoil surface treatments and tip treatments (e.g. bulb, winglets). Generally suppression is achieved through the increase of the vortex core radius (Platzer and Souders 1979, Souders and Platzer 1981). Active cavitation control can be achieved through mass injection into the core of the vortex (Platzer and Souders 1979, Souders and Platzer 1981). This form of cavitation suppression is the object of study for this effort. In the study conducted by Souders and Platzer (1981), water at 40% Dissolved Oxygen taken from the test facility was injected back into the tip flow. An elliptic foil with a modified NACA 66 section was used in flows with Reynolds numbers order of 10 6 . Souders and Platzer (1981) defined cavitation inception as the first appearance of cavitation, generally observed at one chord-length downstream from the foil as the free stream pressure was reduced. They observed that mass injection near the tip region delayed the onset of cavitation reducing the incipient cavitation number by as much as 40%. Injection of high-molecular weight polymer solutions have also been shown to have a cavitation suppression effect (Ting 1974). In the subsequent studies of TVC suppression, active and passive injection of a mass included the use of polymer solutions. Fruman and Afalo (1989) and Fruman et al (1995) studied TVC suppression by using elliptical plan-form hydrofoils at Reynolds number of order 10 5 to 10 6 . They examined injection 500 wppm and 1000 wppm solutions of Polyox WSR-301, water, and a water-glycerin mix. Cavitation densinense was used as a measure of TVC suppression. It was found that there was no significant gain in TVC suppression when injecting water or water-glycerin mix. The injection of a polymer solution, however, did provide a reduction of at least 25% in the inception cavitation number. Laser Doppler Velocimetry measurements were conducted at 0.125, 0.25, 0.5 and 1 chord length from the tip of the foil. It was observed that water or water-glycerin injection modified the axial component of the flow in the core of the vortex, producing a net deficit, but the tangential component remained unchanged. In polymer injection the axial component of the core velocity changed in a similar fashion that observed for to water and water-glycerin injection. The maximum tangential component of the velocity

Incepting cavitation acoustic emissions due to vortex stretching

Abstract: The acoustic signal of cavitation bubbles can be characterized during inception, growth, and collapse Growing and collapsing bubbles produced a sharp, broadband, popping sound However, some elongated cavitation bubbles produced a short tone burst, or chirp, with frequencies on the order of 1 to 6 kHz The frequency content of the acoustic signal during bubble inception and growth were related to the volumetric oscillations of the bubble and vortex dynamics coupling A relationship was also found between the frequency of the oscillations and the flow and water quality conditions INTRODUCTION The static pressure in the core of a linear vortex is depressed when compared with the pressure far from the vortex, and this pressure drop is increased if the vortex is stretched along its axis In some cases, the pressure in the vortex core can fall below the liquid vapour pressure, resulting in a negative cavitation number This can then lead to vortex cavitation if a small bubble or nucleus is present in this area of low pressure Vortex cavitation bubbles may remain small compared with the vortex core radius, with the nearly spherical bubbles rapidly growing and collapsing within the vortex core Or, when the bubble is exposed to a prolonged period of low pressure, the near spherical bubble can expand to fill the core of the vortex and then continue to grow along the vortex axis, becoming highly elongated The growth, splitting, and collapse of vortex cavitation bubbles can produce a variety of acoustic emissions which can relate in complicated ways to the underlying vortical flow, the nature of the nucleus, and the possible presence of a time-varying pressure field in the far field (Chahine 1995; Choi & Chahine 2004; Choi, Hsiao, & Chahine 2004; Choi & Ceccio 2007; Choi, Hsiao, Chahine, & Ceccio 2009) Concentrated regions of vorticity often occur in the tip regions of lifting surfaces immersed in liquid, and they are also associated with the flows within turbo-machinery and with turbulent jets, wakes, and shear layers These are unsteady flows where vortex cavitation typically takes place before the onset of other forms of cavitation, such as, sheet cavitation or cloud cavitation A review of this subject is provided by Arndt (2002) There are many instances in these unsteady flows where weaker or secondary vortices incept before the strongest vortices (ie the vortices with the highest circulation) in the flow This is due to a variety of vortex-vortex interactions occurring between both coand counter-rotating vortices of varying strength that can lead to stretching of smaller and weaker vortex filaments These secondary vortices can produce cavitation at relatively high pressures due to both vortex stretching and axial flow acceleration in the vortex core In the case of shear layers, the streamwise vortices can be an order of magnitude weaker than span wise vortices, but due to vortex interaction, the streamwise vortices will be stretched by the spanwise vortices and have been observed to cavitate well before the stronger spanwise vortices The resulting cavitation inception location can occur at random sites throughout the shear layer (Katz & O’Hern 1986; O’Hern 1990; Golapan, Katz, & Knio 1999; Iyer & Ceccio 2002 Similarly, a recent study of a ducted rotor propulsor at the U S Navy’s Naval Surface Warfare Center Carderock Division (Chesnakas & Jessup 2003; Oweis, Fry, Chesnakas, Jessup & Ceccio 2006a and 2006b) show that the location and inception pressure of the cavitation was associated with the presence of multiple, interacting vortices Moreover, Chesnakas & Jessup (2003) found that, depending on the static pressure surrounding the propulsor, the acoustic signal of the cavitation bubble was quite varied As the static pressure was lowered from a condition of no cavitation, the initial bubble acoustic signatures resemble a “pop”, a sharp broadband peak As the pressure was further lowered the bubble signature took the form of a “chirp” An acoustic chirp was much longer in duration than a pop, and it contained a well-defined tone when compared to the broadband pop The measured tone of a chirp was between 2 kHz to 6 kHz in frequency Vortex cavitation inception resulting in a well defined tone of frequencies lower than the resonant frequency of the bubble has been predicted analytically and numerically for cavitation bubbles in a line vortex by Choi et al (2009) In this study the interactions between a single cylindrical bubble in the core of a line vortex and the surrounding vortical flow were computed, including the redistribution of the vorticity surrounding the bubble due to the volume changes of the bubble It was found that bubbles could undergo radial oscillation, during bubble growth and collapse These radial oscillations would take place