No mesh file was supplied and no generation block was provided

[hhy2022]

I was trying to self-define and solve an advection problem. Below is my input:

[Mesh]
  type = GeneratedMesh #Can generate simple lines, rectangles and rectangular prisms
  dim = 1
  nx = 100
  ny = 10
  xmax = 1
  ymax = 0.1
  displacements = 'disp_x disp_y'
[]

[Problem]
  type = FEProblem
  coord_type = RZ
  rz_coord_axis = X
[]

[Variables]
  [c]
    # Adds a linear Lagrange variable by default
  []
  [u]
  []
[]

[Kernels]
  [advection]
    type = ConservativeAdvection
    variable = u
    velocity = '1 0 0'
    upwinding_type = full
  []
[]

[BCs]
  [./u_injection_left]
    type = InflowBC
    variable = u
    boundary = left
    velocity = '1 0 0'
    inlet_conc = 1
  [../]
  [./allow_mass_out]
    type = OutflowBC
    variable = u
    boundary = right
    value = '1 0 0'
  [../]
[]

[Executioner]
  type = Steady
  solve_type = NEWTON
  # Set PETSc parameters to optimize solver efficiency
  petsc_options_iname = '-pc_type -pc_hypre_type'
  petsc_options_value = 'hypre boomeramg'
[]

[Outputs]
  exodus = true
[]

After running, it gave me an error message:

No mesh file was supplied and no generation block was provided
application called MPI_Abort(MPI_COMM_WORLD, 1) - process 0
Finished: Exit code: 1

I am confused since I did had the mesh block. Is there any wrong with my input?
Besides, if I would like to create a seperate mesh file, how should I do? Those .e file .msh file are produced manually or through some tools? Where can I find the guidance for this part?
Thank you so much for any help.

[loganharbour]

I am confused since I did had the mesh block. Is there any wrong with my input?

There is not necessarily a single object in the [Mesh] block, therefore you must provide it as such:

[Mesh]
  [gm] # any name you want here
    type = GeneratedMesh #Can generate simple lines, rectangles and rectangular prisms
    dim = 1
    nx = 100
    ny = 10
    xmax = 1
    ymax = 0.1
  []

  displacements = 'disp_x disp_y'
[]

Besides, if I would like to create a seperate mesh file, how should I do? Those .e file .msh file are produced manually or through some tools? Where can I find the guidance for this part?

We have many methods for generating a variety of common meshes. See the Mesh system (more importantly, the MeshGenerator objects) here: https://mooseframework.inl.gov/syntax/Mesh/index.html

If you have a specific mesh in mind that you're trying to generate, we can try to point you in the right direction.

[GiudGiud]

I m not sure.
In InflowBC.C can you can register("mooseTestApp" ... to register("MooseApp", ..
and try again?

also it shoud be InflowBC.C (capital C) btw

[GiudGiud]

also if you are just generating a mesh file you can just comment out the boundary conditions. they are not part of the mesh

[hhy2022]

I created mesh file by only using mesh block. Thank you so much for your advice.
Besides, what is the difference between GeneratedMesh and GeneratedMeshGenerator? I am kind of confused since I thought my mesh is simple enough and those two should both work well.

[GiudGiud]

GeneratedMesh was what we used before the mesh generators existed. Now we use the mesh generators, such as GeneratedMeshGenerator.
It was just a different system, still here due to slow deprecation of things to keep some amount of backwards compatibility

[hhy2022]

Thank you so much for your information.