Researches On Atmospheric Modeling And Applications In Near Space

The flight environment of near space(20-100 km)is special.With the rapid development of near space vehicle technology in recent years,the demand for near space environment model is increasing.The atmosphere of near space is closely related to the troposphere and the thermosphere.It is very sensitive to external forced disturbances from above and below,showing complex spatiotemporal variation characteristics.As an important tool for aircraft design,simulation,technical verification and flight guidance to quickly obtain atmospheric parameters,the ambient atmospheric empirical model is mainly used to give the climate change state of atmospheric meteorological parameters.The real atmosphere contains short-term random change information,such as complex atmospheric fluctuation,which sometimes deviates seriously from the average atmospheric climate state.Therefore,it is the most reliable way to improve the applicability of the atmospheric model and meet the development and utilization requirements of aerospace and near space by evaluating and revising the existing model and establishing a new one.In this paper,model evaluation,model modification method research,modeling method research,and simulation of the effects of near space environment on vehicles,are taken as the main research lines to carry out near space model and application research.The research results of this paper have a very high reference value for the field of aerospace,such as aircraft model selection and use,aircraft design,simulation,thermal protection and track planning.The main work of this paper includes the following specific aspects:(1)Aiming at the applicability of USSA976 and nrlmsise-00 model in engineering application,using the temperature data of TIMED / SABER from 2002 to 2016,the temperature data of the commonly used empirical models are evaluated.The applicability of the models at different altitudes in different latitudes were tested by statistically calculating the average temperature deviations,the standard deviation of the temperature deviations,and the distribution of the root mean square error in different latitudes between the model and the observation results.In addition,by calculating the confidence degree of the models under different temperature error bands,the confidence of the models at typical heights in different latitudes were evaluated.For the same model,the model's confidence decreases with the height increases under the same latitude and temperature error band.The confidence decreases with increasing latitude under the same height and temperature error band.(2)In order to improve the accuracy of atmospheric density from NRLMSISE-00,based on the density data of TIMED / SABER from 2002 to 2016,the atmospheric density of NRLMSISE-00 at 20-100 km was corrected for the first time.A bias correction factor dataset is established based on the density differences between the TIMED/SABER data and NRLMSISE-00.Seven height nodes are set in the range 20–100 km.The different scale oscillations of the correction factor are separated at each height node,and the spherical harmonic function is used to fit the coefficients of the different timescale oscillations to obtain a spatiotemporal function at each height node.Cubic spline interpolation is used to obtain the correction factor at other heights.The spatiotemporal correction function proposed in this paper achieves a good correction effect on the atmospheric density of the NRLMSISE-00 model.The correction effect becomes more pronounced as the height increases.After correction,the relative error of the model decreased by 40–50% in July,especially at ±40°N in the 80–100 km region.(3)A global density perturbation modeling method based on satellite density data is proposed in near space.Based on the atmospheric density observed by TIMED/SABER satellite from 2002-2018,the grid data of monthly average and standard deviation are calculated statistically.Based on the grid data,the characteristics of atmospheric density variations are analyzed.While the relative errors of USSA76 are calculated and the distribution of relative errors between USSA76 and SABER are analyzed.In addition,Driven by the grid data,the atmospheric density is characterized as the sum of the monthly average and the large-scale disturbances and small-scale disturbances.The large-scale perturbations and small-scale perturbations are characterized by cosine functions and first-order autoregressive models,respectively.And a global near space atmospheric density model is initially established.By comparing the simulated values of the model with the observervations of the lidar in Dunhuang,the results show that the model values have a good agreement with the observervations,which verifies that the modeling method is feasible.(4)A global perturbation modeling method based on satellite data for thermodynamic parameters such as atmospheric density,temperature and pressure in the near space is proposed.Based on the thermodynamic parameters observed by TIMED/SABER satellite from 2002-2018,the grid data of monthly average and standard deviation are calculated statistically.On the basis of the previous method of atmospheric density modeling,the perturbations of thermodynamic parameters of different scales were characterized by standard deviation,and the reference atmospheric model of thermodynamic parameters in global near space was established.The feasibility of this modeling method was demonstrated by comparing the simulation values with the lidar observations.For the states of thermodynamic parameters on a given trajectory,Monte Carlo method can traverse all possible states of thermodynamic parameters along a given trajectory,which is very important for aircraft simulation and refinement design.(5)A method for modeling the atmospheric wind field over a single station is proposed.Based on the wind data of MF radar over Langfang,the monthly mean and standard deviations of wind are obtained.The diurnal / semidiurnal tides and planetary waves of 5d,10 d,16d and 23 d were extracted by nonlinear least square method,and the seasonal variation of the amplitude of each component is analyzed.Based on the modeling method of small-scale disturbances in the collaborative modeling of thermodynamic parameters,and considering the correlation between zonal wind and meridional wind,the small-scale disturbances of zonal wind and meridional wind are calculated respectively.Harmonic fitting formulas are used to reconstruct tidal and planetary waves in large-scale disturbances.Large scale and small scale perturbations are superimposed on the basis of monthly average,and an initially reference atmospheric wind model of 82-100 km is initially established.The Monte Carlo method is used to simulate the changes of the atmospheric wind field in July,and the simulations and observations are compared in monthly mean value,standard deviation,monthly mean daily variations,day-to-day variations,and change of gravity wave disturbance with altitude.The results are in good agreement,and the feasibility of the modeling method is verified,which lays a foundation for the establishment of regional/global wind field reference atmospheric model.(6)The effect of atmospheric fluctuation on aerodynamic heat of hypersonic vehicle was studied.It is found that the influence has longitude dependence.Based on the density observed by TIMED/SABER from 2002-2018,atmospheric density influence on aerothermodynamic of hypersonic vehicles is analyzed in 20-80 km.Based on the estimation method of heating transfer on stagnation in engineering,the relationship between the atmospheric density variations and the heating transfer changes is used to analyze the distribution characteristics of heating transfer changes in the vertical and horizontal directions.The results show that: 1)Compared with the heating transfer calculated by USSA76,the heating transfer calculated by monthly mean density of SABER is higher in the middle and high latitudes in the summer hemisphere and lower in the winter hemisphere.There is a maximum value of heating transfer increments around 80 km in high latitudes of summer.The maximum value of heating transfer increments in the southern hemisphere is higher than that of the northern hemisphere.Especially in January of southern hemisphere,the maximum value can reach 32.2%.In the longitude direction,the distribution of heat transfer in the summer hemisphere shows a small difference,while the heating transfer distribution in the winter hemisphere is significantly different.Considering disturbances in the real atmosphere,the heating transfer predicted by SABER is higher than that of USSA76 by up to 40.7% and 36.6% in summer of the southern and northern hemispheres around 80 km,respectively.In the longitude direction,the distribution of heating transfer caused by atmospheric disturbance is significantly different.Therefore,the effects of atmospheric disturbances on hypersonic vehicles cannot be ignored in the design progress.