/PROP/TYPE34 (SPH)
Block Format Keyword Describes SPH property set.
Format
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

/PROP/TYPE34/prop_ID or /PROP/SPH/prop_ID  
prop_title  
m_{p}  q_{a}  q_{b}  ${\alpha}_{\mathit{cs}}$  skew_ID  h_ID  
order  h  ${\xi}_{\mathit{stab}}$ 
Definition
Field  Contents  SI Unit Example 

prop_ID  Property
identifier (Integer, maximum 10 digits) 

prop_title  Property
title (Character, maximum 100 characters) 

m_{p}  Mass of the
particles. (Real) 
$\left[\text{kg}\right]$ 
q_{a}  Quadratic bulk
viscosity. Default = 2.0 (Real) 

q_{b}  Linear bulk
viscosity. Default = 1.0 (Real) 

${\alpha}_{\mathit{cs}}$  Conservative smoothing
coefficient. (Real) 

skew_ID  Skew identifier to define
the initial orthotropic directions in the case of
skew_ID ≠ 0 (means property is
orthotropic). (Integer) 

h_ID  Smoothing length change
based on volume. 6
(Integer) 

order  SPH correction order.
(Integer) 

h  Smoothing
length. Default: see 2 (Real) 
$\left[\text{m}\right]$ 
${\xi}_{\mathit{stab}}$  Coefficient for solving
tensile instability. Default = 0.0 (Real) 
Example (Bird Strike)
#RADIOSS STARTER
#12345678910
/PROP/TYPE34/3000001
BIRD_sphv1 (unit kg_mm_ms) data from Example 49  Bird Strike on Windshield
# mp qa qb alpha_cs skew_ID h_ID
1.725149E4 2E30 1E30 0 0 0
# order h xi_stab
0 6.286 0
#12345678910
#ENDDATA
#12345678910
Comments
 The recommended SPH cell distribution is face centered cubic which can be created in the HyperMesh SPH panel or hexagonal compact net distribution using a Tcl script available from Altair Connect.
 Default value for smoothing
length is set as:
(1) $$h={\left(\frac{{m}_{p}\sqrt{2}}{\rho}\right)}^{\frac{1}{3}}$$which corresponds to the interparticles distance when the particles distribution is hexagonal compact.
For face centered cubic and hexagonal compact net distribution, the recommended smoothing length $h$ is the pitch entered when generating the SPH particles.
 The kinetic energy absorbed by conservative smoothing of velocities is output as hourglass energy into /TH/PART files.
 If
${\xi}_{\mathit{stab}}$
is not equal to zero, an artificial stress is
added to solve the tensile instability, proposed by:
J.J. Monaghan, SPH without a Tensile Instability, Journal of Computational Physics, vol. 159, pp. 290311, 2000
A value of ${\xi}_{\mathit{stab}}=0.3$ is recommended.
 If the sphpart_ID is
used with Sol2SPH option, (in /PROP/SOLID),
$h$
must be input. The mass of the particle can be
0.0 (it is automatically calculated by Radioss). A
good value of the smoothing length is:
(2) $$h=\frac{1.5l}{Ndir}$$Where, $h$
 Smoothing length
 $l$
 Size of the brick elements
 $Ndir$
 Number of particle per direction for each solid element
 The smoothing length on
each particle is updated during the computation according to the change in the
volume.If h_ID=0, the change in the volume is based on three dimensions:
(3) $$\frac{dh}{h}=\frac{1}{3}\frac{dVol}{Vol}=\frac{1}{3}div\overrightarrow{V}dt$$If h_ID=1, the change in the volume is based on one dimension:(4) $$\frac{dh}{h}=\frac{dVol}{Vol}=div\overrightarrow{V}dt$$