CN111595549B - Method, device, equipment and storage medium for measuring ultralow rail resistance coefficient - Google Patents
Method, device, equipment and storage medium for measuring ultralow rail resistance coefficient Download PDFInfo
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Abstract
The application discloses a method, a device, equipment and a storage medium for determining an ultra-low orbit resistance coefficient, wherein the method comprises the steps of firstly calculating the resistance coefficient of an incoming flow atmosphere at a preset speed based on the obtained aerodynamic force of the incoming flow atmosphere at a preset incident angle with a measuring plane; and secondly, calculating the resistance coefficients at different incoming flow speeds based on the expressions of the resistance coefficients at different incoming flow speeds and the resistance coefficients of the atmosphere flowing at a preset speed to the measuring plane. The resistance coefficient of the measuring plane flowing down atmosphere at the preset speed is convenient and simple to measure, the resistance coefficient under the flowing speed condition which cannot be achieved under the test condition can be conveniently obtained through the popularization of a formula, and then the actual ultra-low rail atmospheric resistance of the aircraft can be easily obtained.
Description
Technical Field
The invention relates to the technical field of aerodynamic force of ultra-low rail rarefied gas and aircraft action, in particular to a method, a device, equipment and a storage medium for measuring an ultra-low rail atmospheric resistance coefficient.
Background
Lean gas dynamics have an important background of application in the aerospace field. The atmosphere in the LEO orbit and the adjacent space is very thin and cannot support the normal life activities of human beings, but the atmosphere can cause great influence on the spacecraft flying at high speed in the orbit. The impact of the high-speed moving atoms on the spacecraft can increase the aerodynamic resistance of the spacecraft, so that the orbit of the aircraft descends and even crashes, and the service life of the aircraft is shortened.
Due to the rarefaction effect, the conventional continuous medium assumption is not established, so that the N-S equation for processing continuous flow is not applicable any more, and the aerodynamic force and the thermal effect of rarefaction gas on the wall surface cannot be calculated by using the N-S equation. The scholars commonly use the drag coefficient to calculate the aerodynamic drag experienced by the aircraft. The drag coefficient is a calculation parameter capable of quickly and approximately calculating the ultra-low rail atmospheric drag suffered by the aircraft, and has important significance for the design and the service life evaluation of the aircraft.
Although there are recent molecular simulation methods for calculating aerodynamic drag, the aerodynamic drag experienced by an aircraft is calculated, for example, using the Monte Carlo (MC) or direct Monte Carlo (DSMC) methods. However, the reflection model dealing with molecular and wall interactions in the Monte Carlo (MC) method is not yet mature. The reflection model of the action of the rarefied gas and the wall surface comprises a mirror reflection model, a diffuse reflection model (DRIA) with incomplete energy adaptation, an object plane reflection model (CLL), a Maxwell model and the like. The mirror reflection means that the particles are directly reflected out of the mirror without energy exchange with the wall surface. Diffuse reflection means that incident molecules are in complete thermal adaptation with the surface of the material, and the molecules are spatially reflected in the form of diffuse reflection. The diffuse reflection model (DRIA) means that the random distribution probability of the velocity direction of the reflecting molecules is the same, but the thermal adaptation degree of the reflecting molecules to the surface of the material is variable. The object plane reflection model (CLL) provides distribution functions for normal and tangential components of the reflected molecule velocity, and the main parameters of the distribution functions are normal energy adaptive coefficients and tangential energy adaptive coefficients.
The Maxwell model (Maxwell) is the superposition of specular and diffuse reflection, which assumes that particles of alpha are diffuse reflection while accommodating the wall temperature, and particles of 1-alpha are specular reflection. It is easy to see that specular reflection and diffuse reflection are extreme reflection models and do not describe well the action reflection behavior of molecules and walls. The object plane reflection model (CLL) is physically more realistic, but it contains two adaptive parameters, namely tangential and normal, and the two parameters have certain coupling, so that the parameters are difficult to measure, and therefore, the object plane reflection model (CLL) is difficult to be practically applied.
The Maxwell model (Maxwell) is the most widely applied model with better effect at present. The adaptive coefficient in the Maxwell model (Maxwell) is influenced by various aspects such as material characteristics, roughness, inflow gas properties, speed and the like, and no data reference is available at all times. Researchers either take empirical parameters, such as 0.5 and 0.9, to do the study, or directly take 0 and 1 for both extreme conditions to give an envelope. Therefore, the parameter α in the Maxwell model (Maxwell) becomes a key parameter that restricts the calculation accuracy. Therefore, the ultralow rail resistance coefficient is difficult to determine by adopting the Monte Carlo simulation method, the application range is limited, and the method is not mature enough.
Disclosure of Invention
In view of the above-mentioned drawbacks and deficiencies in the prior art, it is desirable to provide a technical solution for determining the coefficient of drag of the aerodynamic drag of the incoming flow of an ultra-low orbit aircraft during flight to obtain the aerodynamic drag of the aircraft. The scheme is that the aerodynamic resistance of the concerned material and the gas characteristic working condition is obtained by adopting an experimental means, and the atmospheric resistance coefficient is obtained by combining the basic aerodynamic equation of the rarefied gas dynamics.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for measuring an ultra-low rail resistance coefficient, comprising:
calculating a resistance coefficient of the incoming flow atmosphere at a preset speed based on the obtained aerodynamic force of the incoming flow atmosphere at a preset incident angle with the measuring plane;
and calculating the resistance coefficients at different incoming flow speeds based on the expression of the resistance coefficients at different incoming flow speeds and the resistance coefficient of the air flowing at a preset speed to the measuring plane.
In one embodiment, the step of calculating the resistance coefficients at different incoming flow velocities based on the expression of the resistance coefficients at different incoming flow velocities and the resistance coefficient of the atmosphere flowing at a preset velocity to the measurement plane comprises:
deducing to obtain expressions of the resistance coefficients under different incoming flow speeds based on a gas momentum equation of the rarefied gas and an aerodynamic force calculation formula of the resistance coefficients;
substituting the resistance coefficient of the incoming flow atmosphere at the preset speed to the measuring plane into the expression of the resistance coefficient at different incoming flow speeds, and calculating the resistance coefficient at different incoming flow speeds.
In one embodiment, the step of deriving an expression for the drag coefficient at different incoming flow velocities based on the gas momentum equation for the lean gas and the aerodynamic force calculation formula for the drag coefficient comprises:
obtaining an expression of pressure acting on the plane of the aircraft based on a gas momentum equation of the rarefied gas;
and deriving the expression of the resistance coefficient under different incoming flow speeds based on the pressure expression and the aerodynamic force calculation formula of the resistance coefficient.
In one embodiment, substituting the resistance coefficient of the incoming flow atmosphere at the preset speed to the measurement plane into the expression of the resistance coefficients at different incoming flow speeds, and the step of calculating the resistance coefficients at different incoming flow speeds comprises:
determining the correction relation between the resistance coefficients at different incoming flow speeds and the resistance coefficient of the descending air at a preset speed to a specific plane;
and calculating resistance coefficients at different incoming flow speeds based on the correction relation and the resistance coefficient of the downstream air at the preset speed to the measurement plane.
In one embodiment, the step of calculating the coefficient of resistance of the incoming atmosphere at a preset speed based on the obtained aerodynamic force of the incoming atmosphere at a preset angle of incidence to the measurement plane comprises:
measuring aerodynamic force of incoming flow atmosphere with a preset incident angle on a measuring plane at a preset speed;
calculating a pressure on the measurement plane based on the aerodynamic force of the measurement plane;
and obtaining the resistance coefficient of the incoming flow atmosphere at a preset speed based on an aerodynamic force calculation formula of the pressure and the resistance coefficient on the measuring plane.
The invention provides a device for measuring the ultra-low rail resistance coefficient, which is characterized by comprising a resistance coefficient calculation module at a preset speed and resistance coefficient calculation modules at different incoming flow speeds;
the resistance coefficient calculation module at the preset speed is used for calculating the resistance coefficient of the incoming flow atmosphere at the preset speed based on the obtained aerodynamic force of the incoming flow atmosphere at the preset incidence angle with the measuring plane;
and the resistance coefficient calculation module at different inflow speeds is used for calculating the resistance coefficients at different inflow speeds based on the expressions of the resistance coefficients at different inflow speeds and the resistance coefficient of the atmosphere flowing at a preset speed to the measurement plane.
In a third aspect, the invention provides a computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor implements the method described above when executing the computer program.
In a fourth aspect, the invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the method described above.
Compared with the prior art, the invention has the beneficial effects that:
according to the technical scheme provided by the embodiment of the application, firstly, based on the obtained aerodynamic force of the incoming flow atmosphere with a preset incident angle with a measuring plane, the resistance coefficient of the incoming flow atmosphere at a preset speed is calculated; and secondly, calculating the resistance coefficients at different incoming flow speeds based on the expressions of the resistance coefficients at different incoming flow speeds and the resistance coefficients of the atmosphere flowing at a preset speed to the measuring plane. The measurement of the resistance coefficient of the measuring plane flowing down atmosphere at the preset speed is convenient and simple, and the actual resistance of the ultra-low orbit aircraft can be easily obtained, so that the resistance coefficient is obtained. Through theoretical derivation, a calculation formula of the resistance coefficients at different incoming flow speeds is obtained, and the resistance coefficients in a speed range which cannot be reached by other tests can be obtained through extrapolation of the resistance coefficients at a preset speed.
Drawings
Other features, objects and advantages of the present application will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, made with reference to the accompanying drawings in which:
FIG. 1 is a schematic flow chart of a method for determining an ultra-low rail resistance coefficient according to an embodiment of the present invention;
FIG. 2 is a schematic flow chart illustrating the steps of calculating the resistance coefficient at different incoming flow speeds according to the embodiment of the present invention;
FIG. 3 is a schematic flow chart illustrating the steps of calculating the resistance coefficient at a predetermined speed according to the embodiment of the present invention;
FIG. 4 is a block diagram illustrating an exemplary structure of an apparatus for determining an ultra-low rail resistance coefficient according to an embodiment of the present invention;
FIG. 5 is a schematic block diagram of a computer device suitable for implementing embodiments of the present invention;
fig. 6 is a schematic structural diagram of a three-wire torsional pendulum micro-thrust measurement system according to an embodiment of the present invention.
In the figure: the method comprises the following steps of 1-thrust measuring plate, 2-thrust transfer rod, 3-laser, 4-reflector and 5-scale.
Detailed Description
The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the present invention are shown in the drawings.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.
As mentioned in the background, it is easy to see that specular reflection and diffuse reflection are extreme reflection models and do not describe well the acting reflection behavior of molecules and walls. The object plane reflection model (CLL) is physically more realistic, but it contains two adaptive parameters, namely tangential and normal, and the two parameters have certain coupling, so that the parameters are difficult to measure, and therefore, the object plane reflection model (CLL) is difficult to be practically applied. The Maxwell model (Maxwell) is a model with a better application effect at present, is the superposition of specular reflection and diffuse reflection, and assumes that alpha particles are suitable for wall temperature and diffuse reflection, and 1-alpha particles are specular reflection. However, the adaptive coefficient in the Maxwell model (Maxwell) is influenced by various aspects such as material characteristics, roughness, incoming flow gas properties, speed and the like, and no data reference is available at all times. Researchers either take empirical parameters, such as 0.5 and 0.9, to do the study, or directly take 0 and 1 for both extreme conditions to give an envelope. Therefore, the parameter α in the Maxwell model (Maxwell) becomes a key parameter that restricts the calculation accuracy. Therefore, the ultralow rail resistance coefficient is difficult to determine by adopting the Monte Carlo simulation method, the application range is limited, and the method is not mature enough.
Therefore, it would be an improvement in the present application to provide a determination scheme that can easily obtain the ultra-low rail drag coefficient actually experienced by an aircraft and can be applied to different materials with various degrees of roughness.
The basic concept of the invention is to firstly obtain the resistance coefficient of the incoming flow atmosphere at a preset speed and at a preset incident angle with a measuring plane, and then calculate the resistance coefficients at different incoming flow speeds based on the expressions of the resistance coefficients at different incoming flow speeds calculated by an aerodynamic force macroscopic integral equation. Based on the above concept, the invention provides a method, a device, equipment and a storage medium for measuring an ultra-low rail resistance coefficient.
Referring to fig. 1, fig. 1 shows a schematic flow chart of the ultra-low rail resistance coefficient provided by the embodiment of the present application. As shown in fig. 1, the method includes:
in step 20, the resistance coefficients at different incoming flow speeds are calculated based on the expressions of the resistance coefficients at different incoming flow speeds and the resistance coefficients of the atmosphere flowing at a preset speed to the measurement plane.
In the above steps, it is necessary to know the resistance coefficient of the gas, which means that when an object moves relatively in the gas, the object will be subjected to the resistance of the gas. The direction of the resistance is opposite to the speed direction of the object relative to the gas, and the magnitude of the resistance is related to the magnitude of the relative speed. The object for which the resistance coefficient of the incoming air at a preset speed is directed is a measurement plane, the measurement plane is arranged in a laboratory, and the incoming air is generated by high-speed jet equipment, such as a rocket engine, a jet pipe and the like. The object for which the drag coefficients at different incoming flow velocities are directed is for an aircraft in a thin gas, and the atmospheric drag is actually caused by the collision of gas molecules, so the basic principle of calculating the aerodynamic force is to consider the thin particles as independent momentum pellets to collide with the wall surface to generate the aerodynamic force. The speed of the aircraft is not constant, and therefore the corresponding drag coefficients are not the same.
Referring to fig. 2, fig. 2 shows a schematic flow diagram of step 10, said step 10 comprising:
102, calculating the pressure on the measuring plane based on the aerodynamic force of the measuring plane;
and 103, obtaining a resistance coefficient of the inflow atmosphere at a preset speed based on a pressure and aerodynamic calculation formula on the measurement plane.
It should be noted that the measurement plane is formed on the thrust measurement plate 1 of the three-line torsional pendulum micro-thrust measurement system, and fig. 6 shows a specific structure of the three-line torsional pendulum micro-thrust measurement system. As shown in fig. 6, the three-wire torsional pendulum micro-thrust measurement system further comprises a thrust transmission rod 2, a laser 3 and a reflecting mirror 4. The thrust survey board 1 is used for receiving the aerodynamic force of incoming flow, and the thrust dowel steel is used for connecting 1 and the torsional pendulum main part with certain installation angle, laser instrument 3 is used for providing incident light, and speculum 4 is used for reflecting incident light.
The following describes a process of measuring aerodynamic force of an incoming flow atmosphere at a preset incident angle on a measurement plane at a preset speed, with reference to a specific structure of a three-line torsional pendulum micro-thrust measurement system.
The step of measuring the aerodynamic force of the incoming flow atmosphere at a preset incident angle to the measurement plane at a preset velocity may comprise:
emitting inflow atmosphere onto the measuring plane along a preset angle, pushing the thrust measuring plate to rotate so as to drive the reflecting mirror to rotate, and enabling the position of reflected light emitted by the laser to move due to the rotation of the reflecting mirror;
and estimating the aerodynamic force provided by the incoming air to the thrust plate based on the displacement of the reflected light. The displacement of the reflected light can be measured by the scale, the reflected light is reflected to the scale 5, and the displacement is obtained through the change of the scale reading.
Preferably, the step of measuring the aerodynamic force of the incoming flow atmosphere at a preset incidence angle to the measurement plane at a preset speed may further include: and adjusting an angle beta between the thrust measuring plate and the thrust transmission rod to measure aerodynamic force under different preset incidence angles.
Specifically, firstly, the inflow atmosphere at a preset speed is measured by a three-wire torsional pendulum micro-thrust measurement system, and aerodynamic force F borne by a measurement plane is measured when the inflow atmosphere is sprayed to the measurement plane at a preset incidence angle theta.
Obtaining the pressure p of the measuring plane on the thrust measuring plate according to the formula (1):
wherein A is the area of the thrust plate.
The aerodynamic force calculation formula based on the inflow atmosphere is as follows:
comparing the formula (1) and the formula (2), the resistance coefficient C of the measuring plane can be obtainedDThe expression of (a) is:
wherein ρ is the incoming flow gas density, U is the normal velocity, F is the aerodynamic force exerted on the measurement plane, a is the area of the thrust measurement plate, and θ is the incident angle.
Because the density rho of the incoming flow gas is fixed, the normal speed U of the incoming flow atmosphere is known, the preset incidence angle theta is set, and the area A of the thrust plate is measured in advance, so that the resistance coefficient of the incoming flow atmosphere to the measuring plane at the preset speed can be obtained.
The aircraft flies at about a first cosmic velocity, about 7.9km/s, and can only reach 3km/s with the jet of chemical thrusters, whereas the lowest stable operating energy is generally about 100eV, corresponding to a minimum of 36km/s, if electric thrusters are used. The 7.9km/s is just in the middle of the vacant area, and the speed cannot be reached by the existing experimental means, so theoretical extrapolation is needed for the ultra-low rail.
Referring to fig. 3, fig. 3 shows a schematic flow chart of step 20. The step 20 comprises:
and 202, substituting the resistance coefficient of the incoming flow atmosphere at the preset speed to the measurement plane into expressions of the resistance coefficients at different incoming flow speeds, and calculating the resistance coefficients at different incoming flow speeds.
It should be noted that, the expression of the resistance coefficient at different incoming flow velocities here refers to a reduced expression which is relatively simple and easy to calculate through theoretical analysis of the reduced formula.
In step 201, deriving expressions of the resistance coefficients at different incoming flow velocities based on a gas momentum equation of the lean gas and an aerodynamic force calculation formula of the resistance coefficients includes:
obtaining an expression of pressure acting on the plane of the aircraft based on a gas momentum equation of the rarefied gas, and deducing to obtain expressions of resistance coefficients under different incoming flow speeds based on the expression of the pressure and an aerodynamic force calculation formula of the resistance coefficients.
Specifically, according to Maxwell's model (Maxwell) in which a thin gas acts on a wall surface, the momentum of the incoming flow and the momentum of the part of the gas that is specularly reflected contribute to aerodynamic force are mainly the momentum, and the diffuse reflection part is negligible due to the small reflection speed. The pressure acting on the aircraft plane can therefore be derived from the gas momentum equation for the rarefied gas as:
wherein ρ is the incoming flow gas density, U is the normal velocity,
for molecular velocity ratio, α is the adaptation coefficient in Maxwell's model (Maxwell), with values between 0-1, erf () is the error function, and R is the gas constant.
erf () is an error function whose expression is:
for aircraft, the speed of flight is often much greater than the thermal motion speed corresponding to the local gas temperature, so S is much greater than 1, at which point S is much greater
Going toward 0, the error function is approximately equal to 1, and equation (4) can be reduced to:
the expression for the drag coefficient at different incoming flow velocities can be written as:
in step 202, the resistance coefficient of the incoming flow atmosphere at the preset speed to the measurement plane is substituted into the expressions of the resistance coefficients at different incoming flow speeds, and the step of calculating the resistance coefficients at different incoming flow speeds includes:
determining the correction relation between the resistance coefficients at different incoming flow speeds and the resistance coefficient of the descending air at a preset speed to a specific plane;
and calculating resistance coefficients at different incoming flow speeds based on the correction relation and the resistance coefficient of the downstream air at the preset speed to the measurement plane.
Specifically, the drag coefficient C for a particular incoming flow velocity obtained by equation (3)DIs represented as CD0C corresponding to the drag coefficient at different incoming flow velocitiesDCan be expressed as:
CD＝kCD0 (8)
it should be noted that k is a correction coefficient, and is used to indicate a correction relationship between the resistance coefficient at different incoming flow velocities and the resistance coefficient of the incoming flow atmosphere at a preset velocity with respect to a specific plane.
Determining a correction coefficient k based on an expression of the resistance coefficients at different incoming flow speeds, wherein the value of the correction coefficient k is as follows:
wherein, U0For experimentally measured characteristic speeds, U is the target speed, α1For the adaptation coefficient of Maxwell model (Maxwell) at the required incoming flow velocity, alpha0The adaptive coefficient of Maxwell model (Maxwell) at preset speed is shown, R is gas constant, T, T0The local gas temperatures at the requested incoming flow velocity and the preset velocity, respectively, then the drag coefficient at the requested incoming flow velocity can be obtained according to equations (8) and (9) as:
wherein, CD0Calculated for equation (3).
The resistance coefficient of 7.9km/s can be deduced by the method.
For ultra-low rail lean atmospheres, which are free molecular flows, T, T at this point0Temperature T of the atmosphere in which both are incoming flowsinWherein T isinTypically a known quantity, and may be found in a table look-up, for example 360K at 120km height. In this case, equation (10) can be simplified as:
the thermal adaptation coefficient in the equation can be obtained by the following equation:
wherein M is the atomic weight of the gas molecule, μ is the molecular weight ratio of the gas molecular atomic weight to the solid atom, TwIs the solid wall temperature.
For simple working conditions of engineering applications, if the wall is a heat-insulating wall, i.e. TwWhen the adaptive coefficient is constant, i.e. alpha, in the formula (11)1＝α0. Equation (11) can be simplified to:
more generally, assuming that the wall is a radiation wall, the temperature of the wall needs to be iteratively calculated, including the steps of:
1) first assume a wall temperature TwCalculating the thermal adaptation coefficient alpha according to the formula (12)0；
2) Calculating the adaptive coefficient alpha of the wall surface0Net input heat flow qin：
In the formula (I), the compound is shown in the specification,
is the molecular velocity ratio, R is the gas constant, T is the incoming flow temperature, and gamma is the gas specific heat ratio;
3) calculating net output heat flow q of wallout：
Wherein epsilon is the emissivity of the object, and sigma is the Stonelman-Boltzmann constant;
4) comparison qinAnd q isoutIf q isin>qoutThen increase TwOtherwise, decrease Tw；
5) Repeating steps 1-4 until qin-qout<error, where error is the set error limit, then T is the timewIs the wall temperature;
after the wall surface temperature is obtained, the heat adaptation coefficient alpha is calculated by substituting the formula (12)0。
Similarly, the thermal adaptive coefficient alpha at the target speed can be obtained by repeating the process1。
After obtaining two thermal adaptation coefficients, substituting the two thermal adaptation coefficients into a formula (11) to obtain a resistance coefficient C at a target speedD1。
Referring to fig. 4, fig. 4 shows an apparatus for determining an ultra-low rail resistance coefficient provided in the embodiments of the present application. The device comprises a resistance coefficient calculation module 401 at a preset speed and a resistance coefficient calculation module 402 at different incoming flow speeds.
The resistance coefficient calculation module 401 at the preset speed is configured to calculate a resistance coefficient of the incoming flow atmosphere at the preset speed based on the obtained aerodynamic force of the incoming flow atmosphere at the preset incident angle with the measurement plane;
the resistance coefficient calculation module 402 at different inflow speeds is configured to calculate the resistance coefficients at different inflow speeds based on expressions of the resistance coefficients at different inflow speeds and a resistance coefficient of the atmosphere flowing at a preset speed to the measurement plane.
Optionally, the resistance coefficient calculation module at different incoming flow speeds includes:
the expression derivation unit of the resistance coefficients at different incoming flow speeds is used for deriving and obtaining expressions of the resistance coefficients at different incoming flow speeds based on a gas momentum equation of the rarefied gas and an aerodynamic calculation formula of the resistance coefficients;
and the resistance coefficient calculation unit under different incoming flow speeds is used for substituting the resistance coefficient of the incoming flow atmosphere under the preset speed to the measurement plane into the expression of the resistance coefficient under different incoming flow speeds, and calculating the resistance coefficient under different incoming flow speeds.
Optionally, the expression derivation unit for the resistance coefficients at different incoming flow speeds includes:
the pressure expression derivation subunit is used for obtaining an expression of the pressure acting on the plane of the aircraft based on a gas momentum equation of the rarefied gas;
and the expression derivation subunit is used for deriving the expressions of the resistance coefficients at different incoming flow speeds based on the pressure expression and the aerodynamic calculation formula of the resistance coefficients.
Optionally, the resistance coefficient calculation unit at different incoming flow velocities includes:
the correction relation determining subunit is used for determining the correction relation between the resistance coefficients at different incoming flow speeds and the resistance coefficient of the downstream air at a preset speed to a specific plane;
and the resistance coefficient calculation subunit is used for calculating the resistance coefficients at different incoming flow speeds based on the correction relation and the resistance coefficient of the downstream air at the preset speed to the measurement plane.
Optionally, the resistance coefficient calculation module at the preset speed includes:
the aerodynamic force measuring unit is used for measuring the aerodynamic force of the incoming flow atmosphere with a preset incidence angle to the measuring plane at a preset speed;
a pressure calculation unit of a measurement plane for calculating a pressure on the measurement plane based on an aerodynamic force of the measurement plane;
and the resistance coefficient calculation unit at the preset speed is used for obtaining the resistance coefficient of the incoming flow atmosphere at the preset speed based on the aerodynamic force calculation formula of the pressure and the resistance coefficient on the measuring plane.
Fig. 5 is a schematic structural diagram of a computer device according to an embodiment of the present invention. As shown in fig. 5, a schematic structural diagram of a computer system 500 suitable for implementing the terminal device or the server of the embodiment of the present application is shown.
As shown in fig. 5, the computer system 500 includes a Central Processing Unit (CPU)501 that can perform various appropriate actions and processes according to a program stored in a Read Only Memory (ROM)502 or a program loaded from a storage section 508 into a Random Access Memory (RAM) 503. In the RAM 503, various programs and data necessary for the operation of the system 500 are also stored. The CPU 501, ROM 502, and RAM 503 are connected to each other via a bus 504. An input/output (I/O) interface 506 is also connected to bus 504.
The following components are connected to the I/O interface 505: an input portion 506 including a keyboard, a mouse, and the like; an output portion 507 including a display such as a Cathode Ray Tube (CRT), a Liquid Crystal Display (LCD), and the like, and a speaker; a storage portion 508 including a hard disk and the like; and a communication section 509 including a network interface card such as a LAN card, a modem, or the like. The communication section 509 performs communication processing via a network such as the internet. A driver 510 is also connected to the I/O interface 506 as needed. A removable medium 511 such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, or the like is mounted on the drive 510 as necessary, so that a computer program read out therefrom is mounted into the storage section 508 as necessary.
In particular, the process described above with reference to fig. 5 may be implemented as a computer software program, according to an embodiment of the present disclosure. For example, embodiments of the present disclosure include a computer program product comprising a computer program tangibly embodied on a machine-readable medium, the computer program comprising program code for performing the above-described method of stand allocation for a plurality of aircraft. In such an embodiment, the computer program may be downloaded and installed from a network through the communication section 509, and/or installed from the removable medium 511.
The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
The units or modules described in the embodiments of the present application may be implemented by software or hardware. The described units or modules may also be provided in a processor. The names of these units or modules do not in some cases constitute a limitation of the unit or module itself.
As another aspect, the present application also provides a computer-readable storage medium, which may be the computer-readable storage medium included in the foregoing device in the foregoing embodiment; or it may be a separate computer readable storage medium not incorporated into the device. The computer readable storage medium stores one or more programs for use by one or more processors in performing the method for stand allocation for a plurality of aircraft described herein.
The above description is only a preferred embodiment of the application and is illustrative of the principles of the technology employed. It will be appreciated by a person skilled in the art that the scope of the invention as referred to in the present application is not limited to the embodiments with a specific combination of the above-mentioned features, but also covers other embodiments with any combination of the above-mentioned features or their equivalents without departing from the inventive concept. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.
Claims (8)
1. A method for determining an ultra-low rail resistance coefficient, comprising:
calculating the resistance coefficient of the incoming flow atmosphere to the measuring plane at a preset speed based on the obtained aerodynamic force of the incoming flow atmosphere at a preset incidence angle with the measuring plane,
calculating the resistance coefficients at different incoming flow speeds based on the expression of the resistance coefficients at different incoming flow speeds and the resistance coefficient of the incoming flow atmosphere to the measuring plane at a preset speed,
coefficient of resistance C of the measuring planeDOThe expression of (a) is:
wherein the content of the first and second substances,
ρ is the incoming flow gas density, U is the normal velocity, θ is the angle of incidence,
in terms of molecular velocity ratio, alpha is an adaptive coefficient in a Maxwell model (Maxwell), the value of the adaptive coefficient is between 0 and 1, R is a gas constant, and T is the local gas temperature under the incoming flow rate;
coefficient of resistance C at the different incoming flow velocitiesDIs expressed as CD＝kCD0，
Substituting the resistance coefficient of the inflow atmosphere at the preset speed to the measuring plane into expressions of the resistance coefficients at different inflow speeds, and calculating the resistance coefficients at different inflow speeds, wherein the steps comprise:
determining a correction relation between the resistance coefficients at different incoming flow speeds and the resistance coefficient of the downstream air at a preset speed to a specific plane, wherein the correction coefficient k is as follows:
and calculating resistance coefficients at different incoming flow speeds based on the correction relation and the resistance coefficient of the downstream air at the preset speed to the measurement plane.
2. The method for determining the ultra-low rail resistance coefficient according to claim 1, wherein the step of calculating the resistance coefficients at different incoming flow speeds based on the expression of the resistance coefficients at different incoming flow speeds and the resistance coefficient of the incoming flow atmosphere to the measuring plane at a preset speed comprises:
deducing to obtain expressions of the resistance coefficients under different incoming flow speeds based on a gas momentum equation of the rarefied gas and an aerodynamic force calculation formula of the resistance coefficients;
substituting the resistance coefficient of the incoming flow atmosphere at the preset speed to the measuring plane into the expression of the resistance coefficient at different incoming flow speeds, and calculating the resistance coefficient at different incoming flow speeds.
3. The method for determining the ultra-low rail resistance coefficient according to claim 2, wherein the step of deriving the expression of the resistance coefficient at different incoming flow velocities based on the gas momentum equation of the lean gas and the aerodynamic force calculation formula of the resistance coefficient comprises:
obtaining an expression of pressure acting on the plane of the aircraft based on a gas momentum equation of the rarefied gas;
and deriving the expression of the resistance coefficient under different incoming flow speeds based on the pressure expression and the aerodynamic force calculation formula of the resistance coefficient.
4. The method of claim 1, wherein the step of calculating the coefficient of resistance of the incoming air at a predetermined speed based on the obtained aerodynamic force of the incoming air at a predetermined angle of incidence with respect to the measurement plane comprises:
measuring aerodynamic force of incoming flow atmosphere with a preset incident angle on a measuring plane at a preset speed;
calculating a pressure on the measurement plane based on the aerodynamic force of the measurement plane;
and obtaining the resistance coefficient of the incoming flow atmosphere at a preset speed based on an aerodynamic force calculation formula of the pressure and the resistance coefficient on the measuring plane.
5. The device for measuring the ultra-low rail resistance coefficient is characterized by comprising a resistance coefficient calculation module at a preset speed and resistance coefficient calculation modules at different incoming flow speeds;
the resistance coefficient calculation module at the preset speed is used for calculating the resistance coefficient of the incoming flow atmosphere to the measuring plane at the preset speed based on the obtained aerodynamic force of the incoming flow atmosphere at the preset incidence angle with the measuring plane;
the resistance coefficient calculation module under different inflow speeds is used for calculating the resistance coefficients under different inflow speeds based on the expression of the resistance coefficients under different inflow speeds and the resistance coefficient of the atmosphere flowing at a preset speed to the measurement plane,
coefficient of resistance C of the measuring planeDOThe expression of (a) is:
wherein the content of the first and second substances,
rho is the incoming flow gas density, U is the normal velocity, theta is the incident angle, the molecular velocity ratio is obtained, alpha is the adaptive coefficient in the Maxwell model (Maxwell), the value is between 0 and 1, R is the gas constant, and T is the local gas temperature under the incoming flow velocity;
coefficient of resistance C at the different incoming flow velocitiesDIs expressed as CD＝kCD0；
The resistance coefficient calculation module under different incoming flow speeds comprises:
the expression derivation unit of the resistance coefficients at different incoming flow speeds is used for deriving and obtaining expressions of the resistance coefficients at different incoming flow speeds based on a gas momentum equation of the rarefied gas and an aerodynamic calculation formula of the resistance coefficients;
and the resistance coefficient calculation unit under different incoming flow speeds is used for substituting the resistance coefficient of the incoming flow atmosphere under the preset speed to the measurement plane into the expression of the resistance coefficient under different incoming flow speeds, and calculating the resistance coefficient under different incoming flow speeds.
6. The apparatus for determining ultra-low rail resistance coefficient according to claim 5, wherein the resistance coefficient calculating module at a preset speed comprises:
the aerodynamic force measuring unit is used for measuring the aerodynamic force of the incoming flow atmosphere with a preset incidence angle to the measuring plane at a preset speed;
a pressure calculation unit of a measurement plane for calculating a pressure on the measurement plane based on an aerodynamic force of the measurement plane;
and the resistance coefficient calculation unit at the preset speed is used for obtaining the resistance coefficient of the incoming flow atmosphere at the preset speed based on the aerodynamic force calculation formula of the pressure and the resistance coefficient on the measuring plane.
7. A computer device comprising a memory and a processor, the memory storing a computer program, wherein the processor when executing the computer program implements the method of any of claims 1-4.
8. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the method of any one of claims 1 to 4.
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