Investigation of wind effects on the design of a mobile radar antenna panel

. This paper presents the static calculation of the mobile radar station antenna fabric design, taking into account the action of its own weight of the load-bearing structure products combined with the load from the limit wind flow. Part of the load-bearing elements are made of the advanced orthotropic material alumoglass plastic, which will allow to significantly gain in weight while maintaining the necessary rigidity and strength. On the basis of aerodynamic calculation, the cases of maximum loading of antenna fabric have been chosen. The possibility of using products made by SLM technology in especially stressed and critical products has been considered.


Introduction
Since many radar stations are based outdoors, such as ground, ship, satellite, airborne, and mobile, one of the loading conditions of any such structure is wind loading created by wind flow.
In this paper, we consider a platform vehicle carrying a container with a rack (taken from the Ground Master 400 installation) on which a radar panel is attached.
The vehicle with the container was considered solely in the aerodynamic calculation for the calculation of air masses movement. The vehicle was taken with overall dimensions: length 8530 mm, width 2500 mm, height 2630 mm with a platform 5774K3 for transportation of type 1C containers. The container contains a rotating rack, to which the radar antennae being examined is attached. Container type 1S with overall dimensions: length 6000 mm, width 2400 mm, height 2600 mm. It has a rack made of 09G2S steel grade.
The aerial canvas consists of the following basic elements: radio transparent shelter, Ibeams (pultrusion profiles), load-bearing metal structures of the aerial canvas made of alumina and the aerial sublattice [1][2][3][4][5]. The possibility of replacing standard, classical materials with composite materials  and the possibility of using additive manufacturing, to produce structural elements using SLM technology [28][29][30][31] as a possibility of automated repair in remote or hard-to-reach areas have been considered [32][33].
The calculations are based on the standard characteristics of the materials used in the construction, adopted in accordance with the reference data. The load bearing steel structures of the antenna plate and the sections forming the antenna sublattice are made of 09G2S steel.

Calculation methodology
The aerodynamic calculations are carried out in Ansys Workbench, module CFX. Loads associated with the weight of the structure and climatic influences are specified as external loading conditions. Based on numerical simulations, wind loads are determined. A vehicle with a container is considered exclusively in the aerodynamic calculation for the calculation of air masses. In particular the influence of the cab and the platform itself on the level and pressure distribution of the wind flow has been considered.

Numerical calculations and results
The wind pressure was determined using the Ansys CFX package used to simulate the flow of liquids and gases, taking into account turbulence [34][35][36][37][38][39][40]. The considered design cases as a function of wind flow direction are shown in Fig. 1. Velocity profile as a function of altitude according to the load and impact code. The distribution of average wind speed U over height z above ground level is determined by the equations: Where w0 -normative value of wind pressure, in Pa, is determined by the type of wind region, and the parameters z0 and α -type of terrain roughness irrespective of the wind region.
As ambient conditions were assumed: temperature -+50°C, atmospheric pressure -630 [mm.m.th.], air humidity -40%, air density -0.856975 [kg/m 3 ], the following air property input parameters were dialed: temperature -+50°C, atmospheric pressure - For the most critical cases of wind loading, a static calculation was carried out in Ansys Workbench, in the Static Structural module.
To perform the static calculation, a detailed model of the antenna plate post (bracket), Fig. 2, with overall dimensions: length 1450 mm, width 1270 mm, height 4180 mm, has been modelled. In order to simplify the overall model, all structural elements considered in the calculation have been designed as surfaces (Shell elements). The subject of the study is the design of the antenna plate, so the bracket has been modelled in a more simplified form. Basket" in which the antennae fabric is located, Fig. 3, with overall dimensions: length 5600 mm, width 1000 mm, height 2600 mm, was simulated.
The antenna panel with overall dimensions of 5500x2300x180 mm, consisting of radar dome (RD), Supporting metal structures of the antenna panel, antenna sub-framework and I-beams (pultrusion profile), Fig. 4.   Fig. 3. Basket containing the antenna web structure mobile radar. Based on the results of the numerical aerodynamic calculation, the maximum pressures created by the airflow on the vehicle with the container with the rack and on the antenna panel were obtained.

Conclusion
The aerodynamic calculation of the wind flow on the object as a whole and on the panels was carried out by mobile radar. In particular, we take into account the influence of the location of the vehicle cab in the vicinity of the antenna panel. The effects of wind flow from different angles of direction relative to the frontal surface of the vehicle and with different calculated cases of location of the antenna plate relative to the frontal surface of the container vehicle are considered.