CP620, Shock Compression of Condensed Matter - 2001 edited by M. D. Furnish, N. N. Thadhani, and Y. Horie © 2002 American Institute of Physics 0-7354-0068-7/02/$ 19.00 PHYSICAL INTREPRETATION OF MATHEMATICALLY INVARIANT K(p,P) TYPE EQUATIONS OF STATE FOR HYDRODYNAMICALLY DRIVEN FLOW George M. Hrbek Los Alamos National Laboratory, Los Alamos, NM 87545 In order to apply the power of a full group analysis(1) to the problem of an expanding shock in planar, cylindrical, and spherical geometries, the expression for the shock front position R[t] has been modified to allow the wave to propagate through a general non-uniform medium. This representation incorporates the group parameter ratios as meaningful physical quantities and reduces to the classical Sedov-Taylor solution for a uniform media. Expected profiles for the density, particle velocity, and pressure behind a spherically diverging shock wave are then calculated using the Tait equation of state for a moderate (i.e., 201TNT equivalent) blast load propagating through NaCl. The changes in flow variables are plotted for Mach < 1.5 Finally, effects due to variations in the material uniformity are shown as changes in the first derivative of the bulk modulus (i.e., K0'). INTRODUCTION DIMENSIONAL ANALYSIS APPLIED TO THE EXPANDING SHOCK FRONT In the companion paper(1) a general solution to the ID hydrodynamic shock wave was given in terms of its group invariance properties. Self-similar profiles for the reduced density, particle velocity, and pressure behind the shock were shown to be explicit functions of the Mach number at the front, the equation of state, the shock formation time, and the uniformity of the material ahead of the shock. In order to illustrate how the group theoretic method can be applied to the investigation of real experiments, this study will consider a moderately strong (M<1.5), spherically diverging shock wave propagating through a solid block of NaCl using the Tait equation of state The traditional Taylor-Sedov dimensional expression for the expanding shock front only allows for an ideal gas, power law non-uniformity. In order to apply the present work into the nonuniform regime for a general material, it is necessary to incorporate a velocity dependence into the expression for the expanding shock front, R[t]. This yields the following ordinary differential equation; R\f\ = (p~lERlt]%-l)(l~*)/(J+l) (t - a}*' (1) Where R'[t] is the velocity of the shock front, t is time, p is the density, E is the energy of the blast, |i is the uniformity of the material ahead of the 115 ∆µ 1 −∆λ ∆2µ∆µ 2(1+J ) ( E1)1 (3+J ) (t −σ−−∆ ) ∆λλ 2 × E E 3+JJ) ) 2(21(+1J+)J ) (3(+ 22 R [t] = ] =22 RRR[i\= [t[]t= ( ( )ρ) ((tt−−σσ)) ρρ −2(λ−1) (2) 0.4 Q 3 0.3 0.3 / 0.2 0.3 0.2 0.1 0.2 0.1 0.1 000 - j -0.1 0 00t -0.1 « -0.1 0 is n j> « * 0.1 0.1 R[t] ——R[t] R[t] R[t] « 0.2 0.2 0 0.3 0.3 A 0.40.4 0.5 ————— Q0.5 5 0.5 «0 « 0.1 0.2 0.3 0.4 Figure Shock Front Position Figure11Shock ShockFront FrontPosition Position Figure 1 Shock Front Position Time (sec.) Time Time (sec.) (sec.) Time (sec.) \ ^-^. ———= R'[t] R'[t] B *• HI" HI- 0.1 0.2 0.3 0.4 fl 1 01 Q3 0A 0.1 0.2 0.3 0.4 0.1 0.2 0.3 0.4 Figure 2 Shock Front Velocity Figure 2 Shock Front Velocity 0.3 00.3 3 0.3 0.4 4 0 0.4 0.4 0.5 0.5 05 0.5 R''[t] R''[t] —R''[t] R"W example, consider the Tait Equation AsAs anan example, consider the Tait Equation ofof of As an example, consider the of (2) As an consider theTait TaitEquation Equation (2)example, (2) State with a shock propagating through NaCl State(2)with withaaashock shock propagating through NaCl State propagating through State with shock propagating throughNaCl NaCland (ρ=2.17 gm/cc, c=2440m/s, Ko=23.81GPa (p=2.17gm/cc, gm/cc, c=2440m/s,Ko=23.81GPa Ko=23.81GPaand and (ρ=2.17 c=2440m/s, (ρ=2.17 gm/cc, (3) (3). c=2440m/s, Ko=23.81GPa and (3) Ko’=5.68) Ko'=5.68) Ko’=5.68) (3).. Ko’=5.68) . We will assume shock wave is produced We will assume thatthat thethe shock wave produced We will assume that the shock wave isis produced We will assume thatequivalent the shock blast wavepropagating is produced a 20 TNT byby 20 tonton TNT equivalentblast blastpropagating propagating by aa20 ton TNT equivalent by a 20 ton equivalent blast propagating through a TNT uniform block of NaCl and through uniform block ofNaCl NaCl and thatthat the the through aauniform block of and that the through a uniform block of NaCl and that the shock takes 5ms to form. shock takes 5ms toform. form. shock takes 5ms to shock takes 5ms toaaform. The choice of such a long formation The choice of such long formation timetime tois to The choice of such long formation time isisto The choice of such a long of formation time isformation to allow graphical illustration ofthe the shock formation allow graphical illustration of the shock allow graphical illustration shock formation allow graphical illustration of the shock formation delay onon thethe same graph asthe the characteristic delay same graph as the characteristic delay on the same graph as characteristic delay on same graph as the characteristic shapes ofthe thethe shock front position over shapes of the shock front position over aa a shapes of shock front position over shapes of the shock front position over a formation reasonably large range oftime. time. Actual formation reasonably large range of Actual formation reasonably large range of time. Actual reasonably large range of time. Actual formation times would of course be much shorter. times would of course be much shorter. times would of course be much shorter. times would of course be much shorter. Figure 4 shows the speed of the shock front asaaas a Figure 4 shows the speed of the shock front as Figure 4 shows the speed of the shock front Figure 4 shows the speed of the shock front as a function of time for such a blast. function of time for such a blast. function of time for such a blast. function of time for such a blast. 2^10.0- H ——R'[t] w "X, ¥ 0.2 0.2 02 0.2 Time (sec.) Time (sec.) Time (sec.) Time (sec.) 20.0 20.0 20.0 1 15.0 15.0 15.0 15.0 10.0 10.0 it JSC 10.0 cn 5.0 *^^—-—*.-————— 5.0 •* i i i i i i ini i i in.... 5.0 0.0 1 a°' 0.0 0( 0.1 0.2 0.3 0.4 01 02 03 04 0.0 1---------_5.0 . . . . . .0.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .^^ 0.4 -5.0 0 -5.0 0 0.1 0.2 0.3 0.4 Figure Figure44u/g[x] u/g[x]For For20 20tons tonsTNT TNT -5.0 1 \ 0.1 0.1 1 0.1 ILLUSTRATIVE EXAMPLE ILLUSTRATIVE EXAMPLE ILLUSTRATIVE ILLUSTRATIVEEXAMPLE EXAMPLE Shock Front Speed Shock Front Speed (km/s) (km/s) Shock Front Speed (km/s) Un-Scaled Shock Un-Scaled Shock Un-Scaled Velocity Shock Velocity Velocity 6 6 65 5 54 4 43 3 32 2 21 1 10 00 0-1 01 -1 -1 0 *^*~^ j__rf-— ^***^^ ^ 00a - 0 -2000 00 -2000 -2000 -4000 Figure Shock Front Acceleration Figure Figure333Shock ShockFront FrontAcceleration Acceleration ———"" Un-Scaled Shock Un-Scaled Shock Un-Scaled Position Shock Position Position I 1 -10000 -10000 -10000 - ————————————————————————— Figure 3 Shock Front Acceleration Time(sec.) (sec.) Time Time (sec.) Time (sec.) ^*-jrf**' <^*^~~ 2000 2000 0 2000 1 -6000 -6000 -8000 -8000 -8000 -10000 Where ∆=2(J+1)/[(J+3)(λ-1)] and the shock posiWhere∆=2(J+1)/[(J+3)(λ-1)] A=2(J+1)/[(J+3)(X-1)]and andthe the shock shock posiposiWhere ∆=2(J+1)/[(J+3)(λ-1)] and the shock posiWhere tion has been shifted so that R[t]=0 at t=σ (the initionhas hasbeen beenshifted shiftedso sothat thatR[t]=0 R[t]=0at t=a(the (the iniinition has been shifted so that R[t]=0 atatt=σ t=σ (the inition tial point where the shock wave forms). tial pointwhere wherethe theshock shockwave waveforms). forms). tial point where the shock wave forms). tial point The group parameters, λ and and (0,, µ,are arerelated relatedthrough through The group parameters, K The group parameters, λ and µ, are related through through The group parameters, λ and µ, are related the invariance of the the energy energyintegral integral(i.e., (i.e.,µ=2µ=2theinvariance invarianceofof of the energy integral (i.e., (1=2the invariance the the energy integral (i.e., µ=2(J+3)λ) and both are ultimately functions of the (J+3)X)and andboth bothare areultimately ultimately functions functions of of the the (J+3)λ) and both are ultimately functions of the (J+3)λ) properties of the propagating medium propertiesofof ofthe thepropagating propagatingmedium medium properties the propagating medium properties Figures 11through through 3are areplots plotsof ofthe theun-scaled un-scaled(i.e., (i.e., Figures through 3 are plots of the un-scaled (i.e., Figures 1 3 Figures 1 term through 3been are plots of theshock un-scaled (i.e., the E/ρ has taken out) front posithe E/ρ E/p term term has has been been taken taken out) out) shock shock front front posiposithe the E/ρvelocity, term has been taken out) shock front position, and acceleration respectively. Note tion,velocity, velocity, and and acceleration respectively. Note tion, acceleration respectively. Note tion, velocity, acceleration respectively. Note that the shock shockand wave takesaaafinite finite amountof time that the wave takes finite amount ofoftime time that wave takes amount that the shock wave takes a finite amount of time to form. to form. form. to to form. a 0.60.6 0.5 0.55 1§ °' 0.5 0.4 0.4 Time(sec.) (sec.) Time (sec.) Time -4000 1 -4000 -4000 -6000 ×× −λ(1+J ) (2) (2) 1+∆ 2 ∆ ∆ ((J + 3)(t −σ − (2σ−)−2(2λ(λ−1−)1µ) µµ (t −σ−−λ)λ(1(1++JJ))µµ µ11)) ++ t −σσ−−(2(σ 3)( 2σ)) )) 22 J J++3)( t− (((( (t(t−−σσ)) )) 0.8 0.8 n fl 0.8 0.7 0.7 0.7 0.6 0.6 Time (sec.) Un-Scaled Shock Un-Scaled Shock Acc. Acc. Un-Scaled Shock Acc. shock, λ is the expansion rate of the shock, σ the shock, σ shock,λformation theexpansion expansion rate of the2shock, shock, the shock time, andrate j=0,of 1,the or for rectangushock, λXisisisthe the expansion rate of the shock, σ0 the the shock formation time, and j=0, 1, or 2 for rectangushock formation time, time, and j=0, j=0, 1,1,geometries or22for forrectangurectangular, cylindrical, and and spherical respecshock formation or lar, and spherical geometries lar,cylindrical, cylindrical, andthis spherical geometries respeclar, cylindrical, and spherical geometries respectively. Note that equation reducesrespecto the tively. Note that this equation reduces to tively. Note that this equation reduces the tively. that for this equationmaterial. reduces to the classicalNote solution a uniform classical solution for a uniform material. classical solution for a uniform material. classical solution for a uniform material. This differential equation has the solution This differential This differentialequation equationhas hasthe thesolution solution This differential equation has the solution 0.5 0 0.5 0.5 \V Figure 4 u/g[x] For 20 tons TNT Figure 4 u/g[x] For 20 tons TNT Figure 2 Shock Front Velocity Figure 2 Shock Front Velocity 116 0.5 05 0.5 0.5 Fromthis this calculationa acorrespondence correspondencebetween between From From thiscalculation calculation a correspondence between the shock speed and time can be determined for the the speed and time can be theshock shock andas time can1. bedetermined determinedfor forthe the blast andisisspeed shown Table blast and shown as Table 1. blast and is shown as Table 1. Particle Velocity (km/s) Particle Velocity (km/s) 1.20 1.20 1.00 1.00 0.80 0.80 0.60 0.60 0.40 0.40 0.20 0.20 0.00 0.00 0.6 0.6 0.6 Table1.1.Shock ShockSpeed Speedfor for a 20tTNT TNT Equiv.Wave Wave Table Table 1.Through Shock Speed foraa20t 20t TNTEquiv. Equiv. Wave Passing NaCl Passing PassingThrough ThroughNaCl NaCl Time after Time Timeafter after(s) Initiation Initiation (s) Initiation 0.20 (s) 0.20 0.20 0.28 0.28 0.28 0.33 0.33 0.33 Mach No.(M) (M) Mach MachNo. No. (M) 1.5 1.5 1.5 1.2 1.2 1.2 1.1 1.1 1.1 6.06.0 0.9 0.9 0.9 Density (gm/cc) Density (gm/cc) 1 Pressure (GPa) Pressure (GPa) 2.02.0 1.01.0 0.00.0 0.60.6 0.70.7 0.80.8 0.8 0.90.9 0.9 Profiles NaCl Figure 7 Pressure NaCl Rgure 7 Pressure Profiles forfor Nad Figure 11 1 CHANGESIN INKo’ Ko’FOR FORNaCl NaCl CHANGES Ko' CHANGES Grouptheory theorymay mayalso alsobebeused usedtotoaid aidininthetheinterinterGroup theory Group interpretationof experiments. pretation ofofexperiments. experiments. pretation (3) (3)(3) reported Asaaacase casein point,Chbabildas Chbabildasand andRuoff Ruoff As case ininpoint, and reported As reported valuesfor forthe theKo’ Ko’ofofNaCl NaClbetween between5.68 5.68and and5.98. 5.98. values for the Ko' values and 5.98. By performing the procedure outlined in this paper, By performing performing the procedure outlined in this By this paper, paper, researchermay maybebeable abletotofind findananinconsistency inconsistency researcher may aaaresearcher theirexperiment experiment bybydetermining determiningthe thedensity, density, inintheir their experiment in density, particle velocity, and pressure profiles behind particle velocity, and pressure profiles behind thethe particle velocity, shock for a specified Mach number using the group shock for a specified Mach number using the group shock for a specified the group theoryrepresentation representationof theflow. flow. theory representation ofofthe the flow. theory Thisisisisbecause becausedifferences differencesin thenumerical numericalvalue value This because differences ininthe the numerical This value ofofthe the material parameters and the thematerial materialparameters parametersand andthe theuniformity uniformityof of uniformity ofof the material ininfront front ofofthe the shock show thematerial materialin frontof theshock shockshow showup quite the upupquite quite clearly asasvariations variations ininthe the calculated clearlyas variationsin thecalculated calculateddensity, density,parparclearly density, particle velocity, and pressure profiles. ticlevelocity, velocity,and andpressure pressureprofiles. profiles. These Thesedifferdifferticle These differences are unique signatures that modify encesare areunique uniquesignatures signaturesthat thatmodify modifyeach eachproproences each profile as the shock slows down. file as the shock slows down. file as the shock slows down. To illustrate this point, calculations reduced Toillustrate illustratethis thispoint, point,calculations calculationsfor forthe the reduced To for the reduced flow variables have been calculated for the range flow variables have been calculated for the range flow variables have been calculated for the range of values for NaCl stated above. of values for NaCl stated above. of values for NaCl stated above. Figures 8-10 show how particle velocFigures8-10 8-10show showhow howthe thedensity, density, particle velocFigures the density, particle velocity, and pressure profiles vary due to changes in the ity, and pressure profiles vary due to changes the ity, and pressure profiles vary due to changes inin the 2.35 2.35 2.25 2.25 0.8 0.8 0.8 11 M=1.1, t=0.33s M=1.1, t=0.33s M=1.2, t=0.28s M=1.2, t=0.28s M=1.5, t=0.20s M=1.5, t=0.20s 3.03.0 M=1.1, t=0.33s M=1.1, t=0.33s M=1.2, t=0.28s M=1.2, t=0.28s M=1.5, t=0.20s M=1.5, t=0.20s 0.7 0.7 0.9 0.9 0.9 Dimensionless Position Dimensionless Position (ξ)(ξ) Dimensionless Position® 4.04.0 Dimensionless Position (ξ) DimensionlessPosition Position Dimensionless (ξ)(£) 2.15 2.15 2.15 0,6 0.6 0.6 0.8 0.8 0.8 5.05.0 Thisanalysis analysishas beencarried carriedout outinin ingenerating generating hasbeen been carried out generating This figures55-7. 5- -7.7. figures 2.55 2.55 2.45 2.45 0.7 0.7 0.7 Figure Velocity 6 Velocity Profiles NaCl Figure forfor NaCl Rgure 6 6 Velocity Profiles Profiles for Nad EachMach Mach numbercorresponds corresponds to a uniquecomcomEach Each Machnumber number correspondstotoaaunique unique compression ratio, β, [Ref. 1, Eq. 30] at the shock pression pressionratio, ratio,β,P,[Ref. [Ref.1,1,Eq. Eq.30] 30]atatthe theshock shock front. Themagnitude magnitudeofof ofthe thecompression compressionisisisdedefront. front. The The magnitude the compression dependent on the particular equation of state (e.g., pendent on the particular equation of state (e.g., pendent on the particular equation of state (e.g., Tait). Following themethodology methodologyoutlined outlinedinininRefRefTait). Tait).Following Followingthe the methodology outlined Reference 1, this compression ratio is used to generate erence erence1,1,this thiscompression compressionratio ratioisisused usedtotogenerate generate the initial conditionsatat atthe thefront frontand andthe thereduced reduced the theinitial initialconditions conditions the front and the reduced equations forf[ξ], f[ξ],g[ξ], g[ξ],and andh[ξ] h[ξ]are aresolved solvednunuequations equationsfor for f[£], g[^], and h[^] are solved numerically from the coupled set of equations [Ref. merically mericallyfrom fromthe thecoupled coupledset setofofequations equations[Ref. [Ref. 1, Eqs. 11-17]. 1,l,Eqs. Eqs. 11-17]. 11-17]. After calculatingthese thesereduced reducedprofiles, profiles,the theactual actual After Aftercalculating calculating these reduced profiles, the actual flow variables are recovered using the following flowvariables variablesare arerecovered recoveredusing usingthe thefollowing following flow scales; scales; scales; For the density Forthe thedensity density For (3) ( ) ρ ξ , t = (3) (ξ , t ) = ρPoρo(t)f(5) ρp(5,t)= (ot()t )f (fξ(ξ) ) (3) andthe thevelocity velocity and (4) R'[t'[]tg] g(ξ(ξ) ) (4) uu«(!,*) (ξ(ξ, t,)t )===RKM*(f) (4) and finally the pressure finallythe pressure pressure and finally 2 (5) (5) (5) PP(ξ(ξ, t,)t )==ρρo (ot()tR) R' ['t[]t2]h[hξ[ξ] ] 2.75 2.75 2.65 2.65 Dimensionless Position (ξ) Dimensionless Position (ξ) M=1.1, t=0.33s M=1.1, t=0.33s 1 ——M=1.1,t=0.33s M=1.2, t=0.28s M=1.2, t=0.28s ——M=1.2,t=0.28s M=1.5, t=0.20s M=1.5, t=0.20s M=1.5,t=0.2Qs 11 Figure5 5Density DensityProfiles Profiles for NaCl Profilesfor forNaCl NaCl Figure Figure 117 material uniformity uniformity parameter (I, µ, and the material parameter Ko', Ko’, for a general spherically diverging shock wave for the asymptotically limiting compression ratio of 1.68 in NaCl. To due this, the initial conditions on the backside of the shock front are computed from the Mach/compression correlation at the front. front. Experimentally, this correlation would be made through regression of the shock front position with time (i.e., R[t]). The Mach number of the front is then used to estimate the compression ratio for a given equation of state at a particular moment of time. The flow variables can then be determined via quadrature of the reduced equations and scaled. Dimensionless Position Position (g) (ξ) Dmensionless Reduced Density f( ) 1.7 1.6 µ=0.0∗ µ=0.5∗ µ=1.0∗ µ=0.0∗∗ µ=0.5∗∗ µ=1.0∗∗ 1.5 1.4 1.3 1.2 1.1 1 0.9 0.91 0.92 0.93 0.94 0.95 0.96 0.97 0.98 0.99 0.9 NaCl Variations for Ko' 568*31*1598** 5.68* and 5.98** Figure 88 Nad Rgure REFERENCES 1 (1) Hrbek, G. M., in Proceedings Shock Compression of Condensed (HI.078), (2001). Condensed Matter-2001 Matter -2001 (H1.078), (2) Kushwah, S.S., and J. Shanker, Physica Physica B B 253, 9095 (1998). (3) Chbabildas, L. C., and and A.L. Ruoff, /. ofAppl. J. of Appl. Phys. 47 (B13), 4182-4187 (1976). Dimensionless Position (ξ) Reduced Velocity g( ) 0.405 0.4 µ=0.0∗ 0.395 µ=0.5∗ 0.39 µ=1.0∗ 0.385 µ=0.0∗∗ 0.38 µ=0.5∗∗ µ=1.0∗∗ 0.37 0.9 0.91 0.91 0.92 0.92 0.93 0.93 0.94 0.94 0.95 0.95 0.96 0.96 0.97 0.97 0.98 0.98 0.99 0.99 0.9 NaCl Variations for Ko' fey foy 568* 5.68* & & 5.98** 5.98** Figure 99 Nad Rgure 0.375 1 Reduced Pressure h( ξ) Dimensionless Position (ξ) Qmensiontess Position (|) 0.4 µ=0.0∗ — ——— jjFQO* 0.38 £- 0.38 3 0.36 µ=1.0∗ —— M-ON ^ fi *3fi | 0.34 0.34 µ=0.0∗∗ — - - jMltO** 1 0.32 0.32 1 0.3 0.3- µ=0.5∗∗ tt µ=1.0∗∗ —— ^"^ s' , '-' ^ x3 '" ^ •^ !^x •» — -, µ=0.5∗ M*5* „ '^* ^-- ^^ r ^ // x<X / X 0.28 0.28 0.9 0 9 0.91 0.92 0.93 0.94 0.95 0.96 0.97 0.98 0.99 1I NaCl Variations for Ko' for 5.68* 5.68* and and5.98** 5.98** Figure 10 Nad Rgure DISCUSSION AND CONCLUSIONS The application of this method is straightforward straightforward and powerful. powerful. It does not require that the total evolution of the flow flow be determined. 118
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