[Alex0815]

Hello everyone,

I tried meshing 2 completely different setups and got the same error both times. At first I thought it was just me doing sth wrong in the meshscript and just couldnt figure it out. Since I just couldnt find any solution i moved on to a very simple setup. Turns out: the EXACT same error message occured again. I wanna highlight that the requested length AS WELL AS the linenum was the same for both setups!

Message: An allocation was made with a negative length requested: -705425008 Filename:FEM_smooth.c Linenum:2399

Screenshot:

Meshscript 1:

! --------------------!
! ----- Header ------ !
! ------------------- !


FINI                    ! exits all old scripts
/ CLEAR                     ! clears workspace
/ PREP7                    ! starts command interface
NACSINIT                 ! starts NACS interface



! ------------------------------------ !
! ----- Definition of variables ------ !
! ------------------------------------ !
elemMode = 'quadr'        ! Quadratic elements = good


! Definition of our Transducer element [Flat at first]

r_emfi = 20e-3                                       ! Radius of the EmFi [ = 20 mm]
h_emfi = 5e-4                                    ! Height of the EmFI [ = 0.5 mm -> Datasheets on EMFIT Site]

! Definition of the Reflector 

r_reflector_i = 50e-3                       ! Inner Radius of the Reflector [ = 50 mm] -> Determined in the corresponding Bachelor Thesis    
w_reflector = 2e-3                                     ! Thickness of the Reflector    [ = 2 mm ] -> Assumption
r_reflector_o = r_reflector_i + w_reflector     ! Outer Radius of the Reflector


! Air  region:
h_air_1 = 5e-4                    ! Height of the Air rectangle in the bottom  [ = 0.5 mm]
r_air_1 = 80e-3                    ! Outer Radius of the Air_bottom area [ = 120 mm]
h_air_2 = 100e-3                ! Height of the middle Air rectangle [ = 500 mm] [first iteration]
r_air_2 = 100e-3                ! Outer radius of the middle Air rectangle [ = 200 mm]

r_air_3 = r_reflector_i                ! Air in the reflector [ = 50 mm]

r_air_4_i = r_reflector_o            ! Air sourrunding the reflector 
r_air_4_o = 100 e-3                
h_air_4 = 100e-3


dx = 85e-6                    ! Meshsize (calculation: dx = c / (20*f) = 343 / (20 * 200000) = 85e-6 m ) [here: may Frequency = 200 kHz]
w_pml = 8*dx                ! Width of the pml region [Used for better results at the outer boundaries of the region]

tol  = dx/5



! ---------------------------------- !
! ----- Create the geometries ------ !
! ---------------------------------- !

! RECTNG , x_min , x_max , y_min , y_max -> rectangle from x_min , y_min to x_max , y_max
! CYL4, X_Center, Y_Center, R_1, Theta_1, R_2, Theta_2

! FIRST THE "Complicated" part of the air region [Cutting the whole into the rectangle]

RECTNG, 0, r_air_2, h_air_1 + h_air_2, h_air_1 + h_air_2 + h_air_4    ! Air Region 4 [Circular has to be substraced from it]
ASEL, s, area, , 1                                                      ! Select Air Region 4
CM, temp1, area

CYL4, 0, h_air_1 + h_air_2, 0, 90, r_reflector_o, 0               ! Air Region 4 [Ciruclar which has to be substracted from Rect.]
ASEL, s, area , ,2                            ! Select Air Region 4 [Circular Part] 
CM,temp2, area

ALLSEL                                    ! Select everything [otherwise ASBA - Area substract Area does not work properly]
ASBA, temp1, temp2                            ! Substracting the inner Part of the AIR AREA to be able to glue and mesh




RECTNG, 0, r_emfi, 0, h_emfi                                         ! EMFI

RECTNG, r_emfi, r_air_1, 0, h_air_1                            ! Air Region 1
RECTNG, 0, r_air_2, h_air_1, h_air_1 + h_air_2                ! Air Region 2 
CYL4, 0, h_air_1 + h_air_2, 0, 90, r_air_3, 0                ! Air Region 3 [Circular] 



CYL4, 0, h_air_1 + h_air_2, r_reflector_i,90,  r_reflector_o, 0        ! Reflector 

RECTNG, r_air_2, r_air_2 + w_PML, h_air_1, h_air_1 + h_air_2 + h_air_4    !PML REGION Right 
RECTNG, 0, r_air_2 + w_PML,h_air_1 + h_air_2 + h_air_4, h_air_1 + h_air_2 + h_air_4 + w_PML !PML REGION Top


! --------------------------------- !
! ----- Connect the geometry ------ !
! ----------------------------------!


ASEL , all
AGLUE , all

! --------------------------- !
! ----- Setup the mesh ------ !
! --------------------------- !

LSEL , all            ! select all lines
LESIZE , all , dx        ! set the meshsize dx on all selected lines


MSHKEY ,2
SETELEMS , 'quadr' , elemMode
ASEL , all
AMESH , all

Meshscript 2:

! --------------------!
! ----- Header ------ !
! ------------------- !


FINI                    ! exits all old scripts
/ CLEAR                     ! clears workspace
/ PREP7                    ! starts command interface
NACSINIT                 ! starts NACS interface



! ------------------------------------ !
! ----- Definition of variables ------ !
! ------------------------------------ !
elemMode = 'quadr'        ! Quadratic elements = good


! Definition of our Transducer element [Flat at first]

r_emfi = 20e-3            ! Radius of the EmFi [ = 20 mm]
h_emfi = 8e-5            ! Height of the EmFI [ = 0.5 mm -> Datasheets on EMFIT Site]


! Air  region:
h_air_1 = h_emfi        ! Height of the Air rectangle in the bottom  [ = Height of EMFI]
r_air_1 = 80e-3            ! Outer Radius of the Air_bottom area [ = 80 mm]
h_air_2 = 60e-3            ! Height of the middle Air rectangle [ = 60 mm] [first iteration]
r_air_2 = 100e-3        ! Outer radius of the middle Air rectangle [ = 100 mm]

h_air_3 = 20e-3            ! Height of the Air rectangle at the top [ = 20 mm]
r_air_3 = r_air_2        ! Radious of the Air rectangle at the top [100 mm]


! Mesh
dx = 80e-6                
w_pml = 8*dx           

tol  = dx/5




! ---------------------------------- !
! ----- Create the geometries ------ !
! ---------------------------------- !
    
RECTNG, 0, r_emfi, 0, h_emfi                                                             

RECTNG, r_emfi, r_air_1, 0, h_air_1                                                    
RECTNG, 0, r_air_2, h_air_1, h_air_1 + h_air_2                                        
RECTNG, 0, r_air_2, h_air_1 + h_air_2, h_air_1 + h_air_2 + h_air_3          


RECTNG, r_air_2, r_air_2 + w_PML, 0, h_air_1 + h_air_2 + h_air_3            
RECTNG, 0, r_air_2 + w_PML, h_air_1 + h_air_2 + h_air_3, h_air_1 + h_air_2 + h_air_3+ w_PML     



! --------------------------------- !
! ----- Connect the geometry ------ !
! ----------------------------------!


ASEL , all
AGLUE , all

! --------------------------- !
! ----- Setup the mesh ------ !
! --------------------------- !

LSEL , all                 ! select all lines
LESIZE , all , dx        ! set the meshsize dx on all selected lines


MSHKEY ,2
SETELEMS , 'quadr' , elemMode
ASEL , all
AMESH , all

I only posted them until meshing - since any further information is not relevant.
It would be really great if someone of you could help me out with this.

BR
Alex

[Alex0815]

Possible solution:

> I resized the Air region since it was unnecesarilly large anyways [atleast for simulation 2]. Doing this seems to have fixed the problem.

> The Error Message still seems kinda strange to me. I'm not sure if this is actually a real solution or just made the regions go away where the problem accured.

Edit: Error Occured again at the same line [2399] after resizing it again