Research Data

Dataset containing characteristics of bubbly shock waves in a cavitating venturi underlying the publication: Gawandalkar U.U., Poelma C. The characteristics of bubbly shock waves in a cavitating axisymmetric venturi via time-resolved X-ray densitometry, Journal of Fluid Mechanics (2024). doi.org/10.1017/jfm.2024.435

Authors: U.U. Gawandalkar (u.u.gawandalkar@tudelft.nl)
         C. Poelma        (c.poelma@tudelft.nl)

Delft University of Technology
Multiphase Systems, Mechanical Engineering
Mekelweg 2, 
2628 CD Delft, 
The Netherlands

Description:
The data in this file contains the characteristics of bubbly shock fronts for different cavitation numbers (sigma). The data is obtained using time-resolved X-ray densitometry, high-frequency pressure and static pressure measurements at the Laboratory for Aero and Hydrodynamics at Delft University of technology and TNO Ypenburg-The Hague in the Netherlands. 
The aim of this work was to investigate the interaction of pressure wave emanating from the cloud implosion with the attached vapour cavity and its effect on vapour shedding leading to cloud cavitation. Furthermore, examine why the vapour shedding mechanism changes from bubbly shock fronts dominated to re-entrant jet driven with increasing cavitation number.

Full details of the study can be found in: Gawandalkar U.U., Poelma C. The characteristics of bubbly shock waves in a cavitating axisymmetric venturi via time-resolved X-ray densitometry, Journal of Fluid Mechanics (2024). doi.org/10.1017/jfm.2024.435

The description of symbols, abbreviations and units are given below:

alpha_1 [-]     --- spanwise integrated pre-shock front vapour fraction
delP    [kPa]   --- pressure rise across the shock after impingement of pressure wave on the attached cavity 
u_sw    [ms^-1] --- the propagation velocity of the condensation shock front after impingement of pressure wave on the attached cavity 
U_t     [ms^-1] --- throat velocity
sigma   [-]     --- cavitation number
c       [ms^-1] --- the speed of sound in the bubbly vaporous attached cavity
Ma_sw   [-]     --- Mach number of the shock front based on u_sw and c
T       [msec]  --- Shedding time period 

alpha_1, delP, u_sw, c, and Ma_sw are phase-averaged over atleast 45 independent vapour shedding cycles.


U_t[ms-1]	sigma[-]   alpha_1[-]   delP[kPa]	u_sw/U_t[-]   c[ms^-1]	  Ma_sw[-]     T[msec]
----------------------------------------------------------------------------------------------------------
13.38     	0.47	    0.68	10400	         0.51	       3.19	  2.13          17.35  
13.54     	0.57	    0.58	10200	         0.48	       3.40 	  1.89          13.57
12.91	        0.67	    0.51	10300	         0.48	       4.25	  1.47          12.50
11.59    	0.78	    0.44	8100	         0.58	       4.62	  1.46          12.10
11.22          	0.84	    0.41	6985             0.56	       5.26	  1.19          10.86
11.15    	0.90	    0.36	6300	         0.47	       5.70	  0.91           9.70

The above table has also been included as .mat file as 'consolidated_data.mat' for the ease of data handling.

The spanwise-avearged time-resolved vapour fraction fields for a single shedding cycle exhibiting the condensation shock front for a case of sigma = 0.47 is included as .mat files: 'time_series_sigma_0_47.mat'.
within this 'time_series_sigma_0_47.mat' file, three different variables are encapsulated: 
XbyD, YbyD are x(axial) and y(radial) coordinates normalised by venturi throat diameter, D = 16.67 mm
alpfa contains 69 instances of vapour fraction fields (alpha(x, y, t)) with a temporal spacing of 1/3600 seconds showing cavitation dynamics.


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A sample code for quick visualisation of time-resolved vapour fractions at sigma = 0.47 with MATLAB ('time_series_sigma_0_47.mat')

figure(1)
    for ii=1:1:69 %where N is the number of images
        I = alpfa(:, :, ii);
        imagesc(XbyD, YbyD, real(I));
        set(gca,'FontSize',19, 'FontName', 'Times');
        set(gcf, 'Position',  [100, 100, 1000, 470.6]);
        xlabel('$x/D_{t} [-]$', 'fontsize', 20, 'FontName', 'Times', 'interpreter','latex' );
        ylabel('$y/D_{t} [-]$', 'fontsize', 20, 'FontName', 'Times', 'interpreter','latex' );
        axis('equal');
        colorbar;
        caxis([0.04, 0.65]);
        pause(0.050);
    end
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Licensing/usage:
Other researchers may use this data in their own work (CC BY 4.0). The dataset is available at the 4TU.Centre for Research Data via, doi.org/10.4121/1975408c-b7ef-4119-8aac-0d3ea2abff8f

Funding:
This work is funded by ERC Consolidator Grant 725183 ‘OpaqueFlows’. 





