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• FORMATION OF THE ATMOSPHERIC ELECTRODE LAYER STRUCTURE

  S.S. Svidelsky, V.S. Litvinova, G. V. Kupovykh, A. G. Klovo

  2021-01-19

  Abstract ▼

  The problem of the formation of the electric state in the lower layer of the atmosphere near
  the Earth's surface is considered in the article. An electrodynamic model of a non-stationary turbulent-
  convective surface layer is investigated in the approximation of the electrode effect. The
  initial system consists of the ionization-recombination equations for aeroions and the Poisson
  equation. Depending on the meteorological conditions in the atmosphere, the cases of classical
  and turbulent electrode effects, as well as the approximation of strong turbulent mixing, are considered
  separately. Turbulent and convective transport, the degree of air ionization, and the presence
  of submicron aerosol particles in the air are factors that affect the space-time structure of the
  electrode layer. Dimensionless parameters (similarity criteria) for electrodynamic equations are
  revealed, which allow choosing the appropriate approximation for modeling the structure of the
  electrode layer depending on atmospheric conditions. In an aerosol-free atmosphere, the time to
  establish a stationary state in the electrode layer is about 5 minutes, for the classical layer (the
  typical height is about 4-5 m), and in the turbulent layer-about 15 minutes. (the typical height is
  about 10 m). In the case of strong turbulent mixing, the distribution scale of electrical quantities
  increases to hundreds of meters. The ratio of the characteristic velocities of turbulent and convective
  processes indicates the predominant physical mechanism of ion transport and the formation of
  the electrode layer structure. An increase in the rate of convective transport directed downwards
  leads to a weakening of the turbulent mixing mechanism, and when moving up, the opposite effect
  occurs. The presence of a submicron aerosol in the atmosphere leads to the formation of heavy
  ions, the mobility of which is much less than that of aeroions. Single-charged aerosol particles
  with a concentration not exceeding the number of aeroions slightly change the spatiotemporal
  characteristics of the electrode layer. While the presence of repeatedly charged aerosol particles
  in the surface air increases the time of electrical relaxation and reduces the height of the electrode
  layer. At sufficiently high concentrations of aerosol (more than the number of aeroions by an order
  of magnitude or more), it is necessary to take into account its transport by turbulentconvective
  flows, and the structure of the electrode layer is determined only by heavy ions.

• MULTIPHYSICS SIMULATION IN ANSYS CFX AND SYSTEM COUPLING OF HEAT TRANSFER INSIDE HERMRTIC CASE OF STRAPDOWN INERTIAL NAVIGATION SYSTEM

  А.А. Medeltsev, P. А. Shapovalov, М. V. Voronov, А. I. Polukhina, P.N. Sigaleva, А.V. Frolov

  2022-04-21

  Abstract ▼

  The article presents a numerical simulation of non-stationary convective-conductive heat
  transfer of the strapdown inertial navigation system (SINS), developed in the JSC «CNIIAG».
  The numerical simulation is carried out in the ANSYS Mechanical. The aim of the study is a comprehensive
  analysis of heat exchange processes, which are characteristic to the device operation,
  including mutual spatial influence of thermal powers on each other, as well as on the block of
  sensitive elements. The simulation of heat transfer inside the hermetic case of the SINS is carried out for critical operating conditions in a strongly and weakly coupled consideration with a comparison
  of both approaches. ANSYS Mechanical, CFX and System Coupling simulation modules
  are chosen for program implementation of each approach. The k-e model of air turbulence with
  implicit consideration of the effect in the boundary layers and diffusion correction in shear flows is
  chosen for this approach. External heat exchange with ambient air is considered by setting convective
  boundary conditions on the external surfaces of the SINS, considering their orientation.
  To obtain numerical values of the heat transfer coefficients, the orientation of each surface in
  space is taken into account by using the appropriate coefficient. The presence of irregularities on
  the surfaces of the SINS in the contacts between solid components is considered by using the calculation
  of thermal resistances of the actual contact and intercontact layer. The simulation results
  of deformed state of SINS structural system, resulting from the action of a non-symmetric thermal
  field, is presented. The analysis of the obtained graphs is carried out. Stiffness indicators of the
  SINS structural system is defined as angles of deviation of sensitivity axes caused by thermal deformations.
  The obtained results make it possible to evaluate the engineering solutions for the
  quality of heat removal from the elements of the PCBs, bypassing the sensitive elements of the
  device, adopted at the stage of product layout.