Stabilization and shock-capturing parameters in SUPG formulation of compressible flows

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1 Comput. Methods Appl. Mech. Engrg. 195 (006) Stabilization and shock-capturing parameters in SUPG formulation of compressible flows Tayfun E. Tezduyar *, Masayoshi Senga Mechanical Engineering, Rice University MS 31, 6100 Main Street, Houston, TX , USA Received 7 October 004; received in revised form 10 January 005; accepted 10 May 005 Abstract The streamline-upwind/petrov Galerkin (SUPG) formulation is one of the most widely used stabilized methods in finite element computation of compressible flows. It includes a stabilization parameter that is known as s. Typically the SUPG formulation is used in combination with a shock-capturing term that provides additional stability near the shock fronts. The definition of the shock-capturing term includes a shock-capturing parameter. In this paper, we describe, for the finite element formulation of compressible flows based on conservation variables, new ways for determining the s and the shock-capturing parameter. The new definitions for the shock-capturing parameter are much simpler than the one based on the entropy variables, involve less operations in calculating the shock-capturing term, and yield better shock quality in the test computations. Ó 005 Elsevier B.V. All rights reserved. Keywords: Compressible flows; Finite element formulation; SUPG stabilization, Stabilization parameters; Shock-capturing parameter 1. Introduction In finite element computation of flow problems, the streamline-upwind/petrov Galerkin (SUPG) formulation for incompressible flows [1,], the SUPG formulation for compressible flows [3 5], and the pressurestabilizing/petrov Galerkin (PSPG) formulation for incompressible flows [6] are some of the most prevalent stabilized methods. Stabilized formulations such as the SUPG and PSPG formulations prevent numerical instabilities in solving problems with high Reynolds or Mach numbers and shocks or thin boundary layers, as well as when using equal-order interpolation functions for velocity and pressure. * Corresponding author. Tel.: ; fax: addresses: tezduyar@rice.edu (T.E. Tezduyar), msenga@rice.edu (M. Senga) /$ - see front matter Ó 005 Elsevier B.V. All rights reserved. doi: /j.cma

2 16 T.E. Tezduyar, M. Senga / Comput. Methods Appl. Mech. Engrg. 195 (006) The SUPG formulation for incompressible flows was first introduced in [1], with further studies in []. The SUPG formulation for compressible flows was first introduced, in the context of conservation variables in [3]. A concise version of that was published as an AIAA paper [4], and a more thorough version with additional examples as a journal paper [5]. After that, several SUPG-like methods for compressible flows were developed. Taylor Galerkin method [7], for example, is very similar, and under certain conditions is identical, to one of the SUPG methods introduced in [3 5]. Later, following [3 5], the SUPG formulation for compressible flows was recast in entropy variables and supplemented with a shock-capturing term [8]. It was shown in [9] that the SUPG formulation introduced in [3 5], when supplemented with a similar shock-capturing term, is very comparable in accuracy to the one that was recast in entropy variables. The stabilized formulation introduced in [10] for advection diffusion reaction equations also included a shock-capturing (discontinuity-capturing) term, and precluded augmentation of the SUPG effect by the discontinuity-capturing effect when the advection and discontinuity directions coincide. A stabilization parameter, known as s, is embedded in the SUPG and PSPG formulations. It involves a measure of the local length scale (also known as element length ) and other parameters such as the element Reynolds and Courant numbers. Various element lengths and ss were proposed starting with those in [1 5], followed by the one introduced in [10], and those proposed in the subsequently reported SUPG-based methods. Here we will call the SUPG formulation introduced in [3 5] for compressible flows (SUPG) 8, and the set of ss introduced in conjunction with that s 8. The s used in [9] with (SUPG) 8 is a slightly modified version of s 8. A shock-capturing parameter, which we will call here d 91, was embedded in the shock-capturing term used in [9]. Subsequent minor modifications of s 8 took into account the interaction between the shock-capturing and the (SUPG) 8 terms in a fashion similar to how it was done in [10] for advection diffusion reaction equations. All these slightly modified versions of s 8 have always been used with the same d 91, and we will categorize them here all under the label s 8-MOD. To be used in conjunction with the SUPG/PSPG formulation of incompressible flows, the discontinuitycapturing directional dissipation (DCDD) stabilization was introduced in [11,1] for flow fields with sharp gradients. This involved a second element length scale, which was also introduced in [11,1] and is based on the solution gradient. This new element length scale is used together with the element length scales already defined in [10]. Recognizing this second element length as a diffusion length scale, new stabilization parameters for the diffusive limit were introduced in [1 14]. The DCDD stabilization was originally conceived in [11,1] as an alternative to the LSIC (least-squares on incompressibility constraint) stabilization. The DCDD takes effect where there is a sharp gradient in the velocity field and introduces dissipation in the direction of that gradient. The way the DCDD is added to the formulation precludes augmentation of the SUPG effect by the DCDD effect when the advection and discontinuity directions coincide. Partly based on the ideas underlying the new ss for incompressible flows and the DCDD, new ways of calculating the ss and shock-capturing parameters for compressible flows were introduced in [14 17]. Like the parameters developed earlier, these new parameters are intended for use with the SUPG formulation of compressible flows based on conservation variables. In this paper, we describe how the new parameters are defined.. Navier Stokes equations of compressible flows Let X R n sd be the spatial domain with boundary C, and (0, T) be the time domain. The symbols q, u, p and e will represent the density, velocity, pressure and the total energy, respectively. The Navier Stokes equations of compressible flows can be written on X and "t (0, T) as ou ot þ of i ox i oe i ox i R ¼ 0; ð1þ

3 T.E. Tezduyar, M. Senga / Comput. Methods Appl. Mech. Engrg. 195 (006) where U =(q,qu 1,qu,qu 3,qe) is the vector of conservation variables, and F i and E i are, respectively, the Euler and viscous flux vectors: u i q 0 u i qu 1 þ d i1 p T i1 F i ¼ u i qu þ d i p ; E i ¼ T i. ðþ B C B u i qu 3 þ d i3 p T i3 A u i ðqe þ pþ q i þ T ik u k Here d ij are the components of the identity tensor I, q i are the components of the heat flux vector, and T ij are the components of the Newtonian viscous stress tensor: T ¼ kð$ uþi þ leðuþ; ð3þ where k and l (=qm) are the viscosity coefficients, m is the kinematic viscosity, and e(u) is the strain-rate tensor: eðuþ ¼ 1 ðð$uþþð$uþt Þ. ð4þ It is assumed that k = l/3. The equation of state used here corresponds to the ideal gas assumption. The term R represents all other components that might enter the equations, including the external forces. Eq. (1) can further be written in the following form: ou ot þ A ou i o ox i ox i where K ij ou ox j R ¼ 0; A i ¼ of i ou ; K ou ij ¼ E i. ox j Appropriate sets of boundary and initial conditions are assumed to accompany Eq. (5). ð5þ ð6þ 3. SUPG formulations 3.1. Semi-discrete Given Eq. (5), we form some suitably-defined finite-dimensional trial solution and test function spaces S h U and Vh U. The SUPG formulation of Eq. (5) can then be written as follows: find Uh S h U such that 8W h V h U : W h ou h þ A h ou h ow h i dx þ K h ou h ij dx W h H h dc X ot ox i X ox i ox j C H W h R h dx þ Xn el h ow s SUPG A h ou h k þ A h ou h i o K h ou h ij R h dx X e¼1 X e ox k ot ox i ox i ox j þ Xn el h ow ou h m SHOC dx ¼ 0. ð7þ e¼1 X e ox i ox i Here H h represents the natural boundary conditions associated with Eq. (5), and C H is the part of the boundary where such boundary conditions are specified. The SUPG stabilization and shock-capturing

4 164 T.E. Tezduyar, M. Senga / Comput. Methods Appl. Mech. Engrg. 195 (006) parameters are denoted by s SUPG and m SHOC. They were discussed in Section 1 and will further be discussed in Section Space time The space time version of Eq. (7) can be written based on the deforming-spatial-domain/stabilized space time (DSD/SST) formulation introduced in [6,18,19]. The finite element formulation of the governing equations is written over a sequence of N space time slabs Q n, where Q n is the slice of the space time domain between the time levels t n and t n+1. At each time step, the integrations involved in the finite element formulation are performed over Q n. The finite element interpolation functions are discontinuous across the space time slabs. We use the notation ðþ n and ðþþ n to denote the values as t n is approached from below and above respectively. Each Q n is decomposed into space time elements Q e n, where e =1,,...,(n el) n. The subscript n used with n el is to account for the general case in which the number of space time elements may change from one space time slab to another. For each slab Q n, we form some suitably-defined finite-dimensional trial solution and test function spaces ðs h U Þ n and ðvh U Þ n. In the computations reported here, we use first-order polynomials as interpolation functions. The subscript n implies that corresponding to different space time slabs we might have different discretizations. The DSD/SST formulation of Eq. (5) can then be written as follows: given ðu h Þ n, find Uh ðs h U Þ n such that 8Wh ðv h U Þ n : W h ou h þ A h ou h h ow i dq þ K h ou h ij Q n ot ox i Q n ox i ox j W h R h dq þ ðw h Þ þ n ðuh Þ þ n ðuh Þ n dx Q n X þ Xðn elþ n ow h s SUPG A h ou h k þ A h ou h i o e¼1 Q e ox n k ot ox i ox i þ Xðn elþ n ow h ou h m SHOC dq ¼ 0. ox i ox i e¼1 Q e n dq K h ij ou h ox j P n W h H h dp R h Here P n is the lateral boundary of the space time slab. The solution to Eq. (8) is obtained sequentially for all space time slabs Q 0,Q 1,Q,..., Q N 1, and the computations start with ðu h Þ 0 ¼ Uh 0, where U 0 is the specified initial value of the vector U. dq ð8þ 4. Calculation of the stabilization parameters for compressible flows and shock-capturing Various options for calculating the stabilization parameters and defining the shock-capturing terms in the context of the (SUPG) 8 formulation were introduced in [14 17]. In this section we describe those options. For this purpose, we first define the acoustic speed as c, and define the unit vector j as j ¼ $qh k$q h k. ð9þ As the first option in computing s SUGN1 for each component of the test vector-function W, the stabilization parameters s q SUGN1, su SUGN1 and se SUGN1 (associated with q, qu and qe, respectively) are defined by the following expression: s q SUGN1 ¼ su SUGN1 ¼ se SUGN1 ¼ Xn en a¼1 ju h $N a j! 1. ð10þ

5 T.E. Tezduyar, M. Senga / Comput. Methods Appl. Mech. Engrg. 195 (006) As the second option, they are defined as s q SUGN1 ¼ su SUGN1 ¼ se SUGN1 ¼ Xnen a¼1 ðcjj $N a jþju h $N a jþ! 1. ð11þ In computing s SUGN, the parameters s q SUGN, su SUGN and se SUGN are defined as follows: s q SUGN ¼ su SUGN ¼ se SUGN ¼ Dt ; ð1þ where Dt is the time step. In computing s SUGN3, the parameter s u SUGN3 is defined by using the expression s u SUGN3 ¼ h RGN 4m ; ð13þ where h RGN ¼ Xnen a¼1! 1 jr $N a j ; r ¼ $kuh k k$ku h kk. The parameter s e SUGN3 is defined as ð14þ s e SUGN3 ¼ ðhe RGN Þ 4m e ; ð15þ where m e is the kinematic viscosity for the energy equation, h e RGN ¼ Xnen a¼1 jr e $N a j! 1 ; r e ¼ $hh k$h h k ð16þ and h is the temperature. The parameters ðs q SUPG Þ UGN, ðsu SUPG Þ UGN and ðse SUPG Þ UGN are calculated from their components by using the r-switch : 1 ðs q SUPG Þ UGN ¼ 1 1 r; ðs q þ ð17þ SUGN1 Þr ðs q SUGN Þr 1 ðs u SUPG Þ UGN ¼ r; þ þ ð18þ ðs u SUGN1 Þr ðs u SUGN Þr ðs u SUGN3 Þr 1 ðs e SUPG Þ UGN ¼ r. þ þ ð19þ ðs e SUGN1 Þr ðs e SUGN Þr ðs e SUGN3 Þr This r-switch was first introduced in [0]. Typically, r =. As the first option in defining the shock-capturing term, first the shock-capturing viscosity m SHOC is defined: m SHOC ¼ s SHOC ðu int Þ ; where ð0þ s SHOC ¼ h SHOC u cha h SHOC ¼ h JGN ; k$q h b kh SHOC ; ð1þ q ref ðþ

6 166 T.E. Tezduyar, M. Senga / Comput. Methods Appl. Mech. Engrg. 195 (006) h JGN ¼ Xnen a¼1 jj $N a j! 1. ð3þ Here q ref is a reference density (such as q h at the inflow, or the difference between the estimated maximum and minimum values of q h ), u cha is a characteristic velocity (such as u ref or ku h k or acoustic speed c), and u int is an intrinsic velocity (such as u cha or ku h kor acoustic speed c). Typically, u int = u cha = u ref. The parameter b influences the smoothness of the shock-front. It is set as b = 1 for smoother shocks and b = for sharper shocks (in return for tolerating possible overshoots and undershoots). The compromise between the b = 1 and selections is defined as the following averaged expression for s SHOC : s SHOC ¼ 1 ððs SHOCÞ b¼1 þðs SHOC Þ b¼ Þ. ð4þ As another option for calculating the shock-capturing parameter, m SHOC is defined as m SHOC ¼kY 1 k Xn sd i¼1 Y 1 ou h ox i! b= 1 b h SHOC ; ð5þ where Y is a diagonal scaling matrix constructed from the reference values of the components of U: 3 ðu 1 Þ ref ðu Þ ref Y ¼ 0 0 ðu 3 Þ ref 0 0 ; ð6þ ðu 4 Þ ref ðu 5 Þ ref ¼ ouh ot þ A h i ou h ox i ð7þ or ¼ A h ou h i ð8þ ox i and b =1orb =. In a variation of the expression given by Eq. (5), m SHOC is defined by the following expression: m SHOC ¼kY 1 k Xn sd i¼1 Y 1 ou h ox i! b= 1 b ky 1 U h k 1 b h SHOC. ð9þ The compromise between the b = 1 and selections is defined as the following averaged expression for m SHOC : m SHOC ¼ 1 ððm SHOCÞ b¼1 þðm SHOC Þ b¼ Þ. ð30þ Based on Eq. (5), a separate m SHOC can be calculated for each component of the test vector-function W: ðm SHOC Þ I ¼jðY 1 Þ I j X n sd i¼1 Y 1 ou h ox i I! b= 1 b h SHOC ; I ¼ 1; ;...; n sd þ. ð31þ

7 Similarly, a separate m SHOC for each component of W can be calculated based on Eq. (9): X n ðm SHOC Þ I ¼jðY 1 sd Þ I j Y 1 ou h! b= 1 ox i¼1 i I Given m SHOC, the shock-capturing term is defined as S SHOC ¼ Xn el $W h : ðj SHOC $U h ÞdX; X e e¼1 T.E. Tezduyar, M. Senga / Comput. Methods Appl. Mech. Engrg. 195 (006) jðy 1 U h Þ I j 1 b b h SHOC ; I ¼ 1; ;...; n sd þ. ð3þ where j SHOC is defined as j SHOC = m SHOC I. As a possible alternative, it is defined as j SHOC = m SHOC jj. If the option given by Eq. (31) or Eq. (3) is exercised, then m SHOC becomes an (n sd +) (n sd + ) diagonal matrix, and the matrix j SHOC becomes augmented from an n sd n sd matrix to an (n sd (n sd + )) ((n sd +) n sd ) matrix. To preclude compounding, m SHOC can be modified as follows: m SHOC m SHOC switchðs SUPG ðj uþ ; s SUPG ðjj uj cþ ; m SHOC Þ; ð34þ where the switch function is defined as the min function or as the r-switch used earlier in this section. For viscous flows, the above modification would be made separately with each of s q SUPG, su SUPG and s e SUPG, and this would result in m SHOC becoming a diagonal matrix even if the option given by Eq. (31) or Eq. (3) is not exercised. ð33þ 5. Test computations The test computations were carried out by using the space time SUPG formulation described in Section 3.. We used two steady-state, inviscid test problems: oblique shock and reflected shock. These were y line plots M =.0 Shock 10 M = x Fig. 1. Oblique shock. Problem description.

8 168 T.E. Tezduyar, M. Senga / Comput. Methods Appl. Mech. Engrg. 195 (006) used in many earlier publications, and here we compute each of them with two different options for the shock-capturing parameter. In the option denoted by CY1, we use Eq. (5) with Eq. (30), and in the option denoted by CYU1, Eq. (9) with Eq. (30). In both options, we use for the expression given by Eq. (8), and set j SHOC = m SHOC I. With both options, as stabilization parameters, we use Eq. (11), and in Eqs. (17) (19) we do not include s SUGN. In both problems, the time-step size is The num- 1.6 CY1 1.5 τ 8-MOD with δ 91 Exact solution 1.4 Density y CYU1 τ 8-MOD with δ 91 Exact solution 1.4 Density y Fig.. Oblique shock. Density along x = 0.9, obtained with CY1 (top) and CYU1 (bottom), compared with the solution obtained with the s 8-MOD and d 91 combination.

9 ber of time steps, nonlinear iterations, and the inner and outer GMRES iterations are 100, 3, 30, and, respectively. The results are compared to those obtained with the s 8-MOD and d 91 combination. The version of s 8-MOD used in this paper for comparison is similar to the one given in [1]: s 8-MOD ¼ maxð0; fðs a s d ÞÞ; ð35þ where s a ¼ h BGN ; u cc s d ¼ d 91 ðu cc Þ ; u cc ¼ c þ u h $ku h k k$ku h kk ; ð36þ f ¼ T.E. Tezduyar, M. Senga / Comput. Methods Appl. Mech. Engrg. 195 (006) u ccdt=h BGN 1 þ u cc Dt=h BGN ; h BGN ¼ Xnen a¼1 1 $ku h k k$ku h kk $N a!. ð37þ Oblique shock. Fig. 1 shows the problem description. This is a Mach uniform flow over a wedge at an angle of 10 with the horizontal wall. The solution involves an oblique shock at an angle of 9.3 emanating from the leading edge. The computational domain is a square with 0 6 x 6 1 and 0 6 y 6 1. The inflow conditions are given as M =.0, q = 1.0, u 1 = cos10, u = sin10, andp = This results in an exact solution with the following outflow data: M = 1.64, q = 1.46, u 1 = 0.887, u = 0.0, and p = All essential boundary conditions are imposed at the left and top boundaries, slip condition at the wall, and no boundary conditions at the right boundary. The mesh is uniform and consists of 0 0 elements. Fig. shows the density along x = 0.9, obtained with CY1 and CYU1, compared with the solution obtained with the s 8-MOD and d 91 combination. In addition to being much simpler, the new shock-capturing parameters yield shocks with better quality. Reflected shock. Fig. 3 shows the problem description. This problem consists of three flow regions (R1, R and R3) separated by an oblique shock and its reflection from the wall. The computational domain is a rectangle with 0 6 x and 0 6 y 6 1. The inflow conditions in R1 are given as M =.9, q = 1.0, u 1 =.9, u = 0.0, and p = Specifying these conditions and requiring the incident shock to be at an angle of 9 results in an exact solution with the following flow data: R: M =.378, q = 1.7, u 1 =.619, u = 0.506, and p = 1.58; R3: M = 1.94, q =.687, u 1 =.401, u = 0.0, and p =.934. All essential boundary conditions are imposed at the left and top boundaries, slip condition at the wall, and no boundary conditions at the right boundary. The mesh is uniform and consists of 60 0 elements. Fig. 4 shows the density along y = 0.5, obtained with CY1 and CYU1, compared with the solution obtained with the s 8-MOD and d 91 combination. Again, the new, much simpler shock-capturing parameters yield shocks with better quality. y M =.378 M =.9 line plots 1 9 Shock 3 3 M = 1.94 x Fig. 3. Reflected shock. Problem description.

10 1630 T.E. Tezduyar, M. Senga / Comput. Methods Appl. Mech. Engrg. 195 (006) CY1 τ 8-MOD with δ 91 Exact solution Density x 3.5 CYU1 τ 8-MOD with δ 91 Exact solution Density x Fig. 4. Reflected shock. Density along y = 0.5, obtained with CY1 (top) and CYU1 (bottom), compared with the solution obtained with the s 8-MOD and d 91 combination. 6. Concluding remarks We described, for the streamline-upwind/petrov Galerkin (SUPG) formulation of compressible flows based on conservation variables, new ways for determining the stabilization and shock-capturing parameters. The stabilization parameter, which is typically known as s, plays an important role in determining the accuracy of the solutions. The shock-capturing term provides additional stabilization near the shocks,

11 T.E. Tezduyar, M. Senga / Comput. Methods Appl. Mech. Engrg. 195 (006) and how the shock-capturing parameter it involves is defined influences the quality of the solution near the shocks. These new ways of calculating the ss and shock-capturing parameters are partly based on the ideas underlying the ss and and DCDD stabilization developed for incompressible flows. Compared to the earlier shock-capturing parameter that was derived based on the entropy variables, the new ones are much simpler, involve less operations in calculating the shock-capturing term, and gave better shock resolution in the test computations we carried out. Acknowledgements This work was supported by the US Army Natick Soldier Center (Contract No. DAAD16-03-C-0051), NSF (Grant No. EIA ), and NASA Johnson Space Center (Grant No. NAG9-1435). References [1] T.J.R. Hughes, A.N. Brooks, A multi-dimensional upwind scheme with no crosswind diffusion, in: T.J.R. Hughes (Ed.), Finite Element Methods for Convection Dominated Flows, AMD-vol. 34, ASME, New York, 1979, pp [] A.N. Brooks, T.J.R. Hughes, Streamline upwind/petrov Galerkin formulations for convection dominated flows with particular emphasis on the incompressible Navier Stokes equations, Comput. Methods Appl. Mech. Engrg. 3 (198) [3] T.E. Tezduyar, T.J.R. Hughes, Development of time-accurate finite element techniques for first-order hyperbolic systems with particular emphasis on the compressible Euler equations, NASA Technical Report NASA-CR-0477, NASA, 198, Available from: < [4] T.E. Tezduyar, T.J.R. Hughes, Finite element formulations for convection dominated flows with particular emphasis on the compressible Euler equations, in: Proceedings of AIAA 1st Aerospace Sciences Meeting, AIAA Paper , Reno, Nevada, [5] T.J.R. Hughes, T.E. Tezduyar, Finite element methods for first-order hyperbolic systems with particular emphasis on the compressible Euler equations, Comput. Methods Appl. Mech. Engrg. 45 (1984) [6] T.E. Tezduyar, Stabilized finite element formulations for incompressible flow computations, Adv. Appl. Mech. 8 (199) [7] J. Donea, A Taylor Galerkin method for convective transport problems, Int. J. Numer. Methods Engrg. 0 (1984) [8] T.J.R. Hughes, L.P. Franca, M. Mallet, A new finite element formulation for computational fluid dynamics: VI. Convergence analysis of the generalized SUPG formulation for linear time-dependent multi-dimensional advective diffusive systems, Comput. Methods Appl. Mech. Engrg. 63 (1987) [9] G.J. Le Beau, T.E. Tezduyar, Finite element computation of compressible flows with the SUPG formulation, in: Advances in Finite Element Analysis in Fluid Dynamics, FED-vol. 13, ASME, New York, 1991, pp [10] T.E. Tezduyar, Y.J. Park, Discontinuity capturing finite element formulations for nonlinear convection diffusion reaction problems, Comput. Methods Appl. Mech. Engrg. 59 (1986) [11] T.E. Tezduyar, Adaptive determination of the finite element stabilization parameters, in: Proceedings of the ECCOMAS Computational Fluid Dynamics Conference 001 (CD-ROM), Swansea, Wales, United Kingdom, 001. [1] T.E. Tezduyar, Computation of moving boundaries and interfaces and stabilization parameters, Int. J. Numer. Methods Fluids 43 (003) [13] T. Tezduyar, S. Sathe, Stabilization parameters in SUPG and PSPG formulations, J. Computat. Appl. Mech. 4 (003) [14] T.E. Tezduyar, Finite element methods for fluid dynamics with moving boundaries and interfaces, in: E. Stein, R. De Borst, T.J.R. Hughes (Eds.), Encyclopedia of Computational Mechanics. vol. 3: Fluids, John Wiley & Sons, 004 (Chapter 17). [15] T.E. Tezduyar, Stabilized finite element methods for computation of flows with moving boundaries and interfaces, in: Lecture Notes on Finite Element Simulation of Flow Problems, Japan Society of Computational Engineering and Sciences, Tokyo, Japan, 003. [16] T.E. Tezduyar, Stabilized finite element methods for flows with moving boundaries and interfaces, HERMIS: Int. J. Comput. Math. Appl. 4 (003) [17] T.E. Tezduyar, Determination of the stabilization and shock-capturing parameters in SUPG formulation of compressible flows, in: Proceedings of the European Congress on Computational Methods in Applied Sciences and Engineering, ECCOMAS 004 (CD-ROM), Jyvaskyla, Finland, 004. [18] T.E. Tezduyar, M. Behr, J. Liou, A new strategy for finite element computations involving moving boundaries and interfaces the deforming-spatial-domain/space time procedure: I. The concept and the preliminary tests, Comput. Methods Appl. Mech. Engrg. 94 (199)

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