CN115993229A - Wind tunnel test method for measuring unsteady aerodynamic coefficient in taking-off and landing process of airplane - Google Patents
Wind tunnel test method for measuring unsteady aerodynamic coefficient in taking-off and landing process of airplane Download PDFInfo
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Abstract
The invention discloses a wind tunnel test method for measuring an unsteady aerodynamic coefficient in the taking-off and landing process of an airplane, and belongs to the technical field of wind tunnel tests. According to the invention, a test model moves according to a preset lifting process in a forced movement mode, the lifting process of a real machine is divided into a plurality of micro-elements, the geometric appearance of the test model is ensured to be similar to that of the real machine, because the wind speed is fixed and unchanged, stokes Ha Ershu in each micro-element time period are equal, namely dimensionless time constants in each micro-element time period are equal, limit indexes such as the maximum pitch angle speed, the maximum heave speed and the like in the lifting process simulation process are obtained through differential calculation, and the limit indexes are compared with test system indexes, so that aerodynamic coefficients influenced by unsteady ground effects in the lifting process of the real machine are directly obtained, and the problem that unsteady aerodynamic coefficients in the lifting process of the real machine cannot be effectively obtained in the traditional ground effect wind tunnel test is solved; has the advantages of strong traceability and high universality.
Description
Technical Field
The invention belongs to the technical field of wind tunnel tests, and particularly relates to a wind tunnel test method for measuring an unsteady aerodynamic coefficient in the taking-off and landing process of an aircraft.
Background
The ground effect is that when the aircraft flies near the ground, the air flow direction bypassing the disturbance of the aircraft is changed by the ground, so that the flow field around the aircraft is changed, and the aerodynamic force and the aerodynamic characteristic are also changed correspondingly. In the take-off and landing process of an aircraft, a ground effect generated by continuously changing the altitude of the aircraft from the ground with time is called an unsteady ground effect. The method has the advantages that the unsteady ground effect in the taking-off and landing process of the aircraft can be studied to help reduce the operation risk of near-ground flight, improve the stability and safety of taking-off and landing of the aircraft, have important significance on the design of the aircraft, have shorter period and lower cost compared with the flight test in wind tunnel tests, have the advantage of reproducibility and the like, and are an important research means for researching the ground effect at present.
The existing ground effect wind tunnel test is mostly simulated according to a steady state, the influences of dynamic parameters such as the heave speed of an airplane model, the continuously-changing ground clearance and the like are not considered, and the research method is applicable when the airplane model is stationary. However, in the actual aircraft taking-off and landing process, the heave speed of the aircraft is continuously changed along with time, and the existing method cannot effectively obtain an unsteady aerodynamic coefficient in the aircraft taking-off and landing process.
Disclosure of Invention
Based on the defects, the wind tunnel test method for measuring the unsteady aerodynamic coefficient in the taking-off and landing process of the aircraft can directly obtain the unsteady aerodynamic coefficient influenced by dynamic parameters such as the model heave speed, the continuously-changed ground clearance and the like in the taking-off and landing process of the aircraft model, is used for analyzing the influence of each dynamic parameter and the ground effect on the taking-off and landing of the aircraft, and solves the problem that the existing method cannot effectively obtain the unsteady aerodynamic coefficient in the taking-off and landing process of the aircraft.
The technology adopted by the invention is as follows: a wind tunnel test method for measuring unsteady aerodynamic coefficient in the taking-off and landing process of an airplane comprises the following steps:
step one: the taking-off and landing processes of the real aircraft are divided into a plurality of micro-elements, the test model is guaranteed to be similar to the geometrical appearance of the real aircraft, and because the wind speed is fixed, the Stokes Ha Ershu in each micro-element time period are equal, namely the dimensionless time constants in each micro-element time period are equal, namely:
in the formula (1)
Is a dimensionless time constant, < >>
Time interval of minute for taking off and landing process of real airplane,/-for real airplane>
Is the real airplane flying speed, & lt + & gt>
Reference length for real aircraft, < >>
A time interval of a trace element of the lifting process of the test model,
For the test model speed, i.e. test wind speed,/->
For the reference length of the test model, the time interval for obtaining the landing process infinitesimal of the test model according to the above formula is as follows:
obtaining the time interval of the taking-off and landing process microelements of the test model through the method (2), further obtaining the motion time process of the test model, and obtaining the attack angle of each time interval of the test model in the wind tunnel through calculation
Angular velocity->
Angular acceleration
Ground height +.>
The parameters of the model are shown as the formula (3) to the formula (6), so that an ideal lifting process of the test model is obtained;
wherein ,
for the angle of attack of a real aircraft per time interval, < >>
The ground clearance height of each time interval of a real airplane;
because the test heave/pitch coupling motion mechanism needs to control the parameters of the ground clearance and the attack angle of the test model at each moment to enable the test model to move in the wind tunnel according to the preset process, the test model process needs to be dispersed into points with the time interval of 0.01s to obtain the ground clearance of the test model
Angle of attack->
The discrete history over time t is then obtained by differential calculationObtaining limit indexes of the maximum pitch angle speed and the maximum heave speed in the process of simulating the lifting process, comparing the limit indexes with test system indexes, if the limit indexes are not met, adjusting the test wind speed, and repeating the process until the lifting process of the test model meets the test equipment indexes;
step two, installing a balance support rod on the heave/pitch coupling motion mechanism, installing a strain balance in the test model, enabling one end of the balance support rod to penetrate through a test model shell and be connected with the strain balance, enabling a measurement end of the strain balance to be connected with an inner cavity of the test model, enabling a data line of the strain balance to be connected with a wind tunnel acquisition system, and installing a side-installed floor near the central position of a wind tunnel opening test section;
step three, under the condition that the wind tunnel stops, adjusting the test model to reach the expected initial attack angle
Height from ground->
Starting a heave/pitch coupling motion mechanism to enable the test model to perform forced motion according to a preset lifting process, acquiring each voltage signal of six-element load of the test model in each process under a windless state by adopting a six-component strain balance, and acquiring voltage signals of attack angle and ground clearance of the test model by adopting an encoder and a height sensor;
and fourthly, starting the wind tunnel, starting the heave/pitch coupling motion mechanism to enable the test model to perform forced motion according to a preset lifting process after the wind speed reaches a preset wind speed, acquiring each voltage signal of six-element load of the test model in each process under the wind-up state by adopting a six-component strain balance, and acquiring voltage signals of attack angle and ground clearance of the test model by adopting an encoder and a height sensor.
And fifthly, processing the acquired six-element load voltage signal data to acquire aerodynamic force and moment load of the test model, firstly, respectively carrying out filtering processing on the original measurement value of the balance acquired in windy and windless states and subtracting corresponding phases, then carrying out iteration of a balance formula and dimensionless processing to obtain six-element aerodynamic coefficients, and finally, respectively converting the voltage signals of the attack angle and the ground clearance of the test model acquired by the encoder and the height sensor into a pitching axis angle signal and a test model height signal.
Furthermore, in the first step, since the actual aircraft is different, the designed take-off and landing processes are also different, and the take-off and landing processes need to be designed according to specific parameters of the actual aircraft: first, the lift coefficient of the ground of a real airplane needs to be determined
Calculating the ground leaving speed V of the real aircraft according to the formula (7) by using parameters of the wing area S l0。
In (7)Wρ is the air density, which is the takeoff weight of the real aircraft.
As engineering estimation, the real aircraft is approximately considered to perform uniform acceleration linear motion in the whole running process, and then the ground running distance of the real aircraft is calculated according to formulas (8) - (9)
And time->
Wherein is a real airplane->
Is a running friction coefficient of (a);
wherein g is the gravity acceleration,
is the average of the available thrust, +.>
。
When calculating the distance and time of the accelerating and ascending section of the real airplane, the speed V of the real airplane when ascending to the height of 15m is considered H =1.3
V l0 Finding the average speed of the aircraft during the whole take-off process +.>
The method comprises the following steps:
searching the maximum available thrust curve graph to obtain the average speed of the accelerating ascending section of the real airplane
Corresponding available thrust
Considering that the climbing angle gamma of the ascending section is not large, the lifting force of a real airplane can be consideredLEqual toWThe corresponding lift coefficient is calculated as:
according to the lift coefficient C corresponding to the real aircraft L Value, find true aircraft resistance coefficient C from take-off pole graph D Calculating the value of the drag D and the average residual thrust (delta T) of the real aircraft av The method comprises the following steps:
obtaining the distance between the accelerating and ascending sections of the real airplane according to the steps (14) - (15)
And time->
，
After the parameters are obtained, the real aircraft attack angle and the horizontal speed are designed, the real aircraft attack angle only changes in the process of lifting the front wheels in the process of taking off, the horizontal speed is uniform acceleration movement in the processes of accelerating running and accelerating rising, and the real aircraft attack angle is increased from 0 DEG to the tail protection attack angle at a uniform speed
Is +.>
Its angular velocity +.>
The obtained horizontal speed of the real airplane comprises the following steps: horizontal velocity of each time interval in the process of accelerating running
And horizontal direction speed of each time interval during acceleration of ascent +.>
, wherein ,/>
Is in the whole take-off process of a real aircraftAnd the design of the actual aircraft course is completed.
Further, the motion center of the heave/pitch coupling motion mechanism coincides with the reference center of the test model.
In the step one, the designed test model lifting process is modified in the area with the aircraft lifting height being more than 1 time of the extension length according to the limitation of the heave/pitch coupling motion mechanism, and acceleration and deceleration sections are added, so that the influence of the heave/pitch coupling motion mechanism on a test is reduced as much as possible while the actual test requirement is met.
The invention has the advantages and beneficial effects that: the invention can simulate the take-off and landing process of the airplane in the wind tunnel, directly obtain the unsteady aerodynamic coefficient influenced by dynamic parameters such as the heave speed, the continuous change of the altitude from the ground and the like in the take-off and landing process of the test model, and is used for analyzing the influence of each dynamic parameter and the ground effect on the take-off and landing of the airplane. According to different types of aircrafts and different test wind speeds, the corresponding take-off and landing process of the test model can be designed, so that the take-off and landing process of the test model is more real, the accuracy of wind tunnel test data is improved, the method has the advantages of high traceability and universality, and a basis is provided for analyzing the influence of each dynamic parameter and ground effect on the take-off and landing of the aircrafts.
Drawings
FIG. 1 is a schematic and schematic diagram of a test device used in the wind tunnel test method of the present invention.
FIG. 2 is a graph of the movement of the angle of attack, height above ground of the test model over time.
FIG. 3 is a graph of the normal force coefficient of the test model over time.
FIG. 4 is a graph of the pitch moment coefficient of the test model over time.
The device comprises a test model 1, a heave/pitch coupling motion mechanism 2, a side-mounted floor 3, a wind tunnel opening test section 4.
Detailed Description
The invention is further described below with reference to the accompanying drawings and examples.
Example 1
As shown in fig. 1, the embodiment discloses a wind tunnel test method for measuring an unsteady aerodynamic coefficient in an aircraft taking-off and landing process, wherein a test model 1 is a dynamic derivative test model with a metal framework and a carbon fiber skin, and the test model 1 performs a forced motion according to a taking-off and landing process of a pre-designed test model 1, so as to simulate the taking-off and landing of a real aircraft and obtain the unsteady aerodynamic coefficient in the taking-off and landing process, and the method specifically comprises the following steps:
step one, the lifting process of the test model 1 is required to be designed before wind tunnel test, and the authenticity of the lifting process of the test model 1 can greatly influence the measurement of test data, so that the method is an important component of the whole test method. Therefore, firstly, the taking-off and landing process of the real aircraft should be obtained as truly as possible to obtain the ground clearance of the real aircraft
Vertical speed->
Horizontal speed->
Aircraft angle of attack->
Over time->
On the basis of which it is converted to obtain the lifting history of the test model 1. The aerodynamic characteristics in the actual airplane take-off and landing processes have certain unsteady time process characteristics, so that the geometrical appearance of the airplane is ensured to be similar to that of the test model 1, and the airplane is required to adopt +.>
Equal to the similarity criterion, the lifting process of the test model 1 is designed by using a dimensionless simulation method. But in the process of taking off and landing of a real airplane, the speed variation range is between 0km/h and 350km/h, and the wind speed in the wind tunnel can not be changed in rapid succession,the similarity criterion of equal strouhal numbers cannot be used simply throughout the take-off and landing history. In order to solve the problems, the concept of infinitesimal is adopted, the take-off and landing processes of the real aircraft are divided into a plurality of infinitesimal, the geometric appearance of the test model 1 is guaranteed to be similar to that of the real aircraft, and the Stokes Ha Ershu in each infinitesimal time period are equal due to the fact that the wind speed is fixed, namely, dimensionless time constants in each infinitesimal time period are equal, namely:
in the formula (1)
Is a dimensionless time constant, < >>
Time interval of minute for taking off and landing process of real airplane,/-for real airplane>
Is the real airplane flying speed, & lt + & gt>
Reference length for real aircraft, < >>
A time interval of a trace element of the lifting process of the test model,
For the test model speed, i.e. test wind speed,/->
For the reference length of the test model, the time interval for obtaining the landing process infinitesimal of the test model according to the above formula is as follows:
acquiring the time interval of the landing process trace of the test model 1 through the method (2), thereby acquiring the operation of the test modelThe dynamic time course is calculated to obtain the attack angle of each time interval of the test model in the wind tunnel
Angular velocity->
Angular acceleration
Ground height +.>
The parameters of the model are shown as the formula (3) to the formula (6), so that an ideal lifting process of the test model is obtained;
wherein ,
for the angle of attack of a real aircraft per time interval, < >>
The ground clearance height of each time interval of a real airplane; since the test system needs to control parameters such as the ground clearance and the attack angle of the test model 1 at each time to move the test model 1 in the wind tunnel according to a predetermined course, it is necessary to obtain the ground clearance of the test model 1 by dispersing the course into points with a time interval of 0.01s>
Angle of attack->
And obtaining limit indexes such as the maximum pitch angle speed, the maximum heave speed and the like in the process of simulating the lifting process according to the discrete process changed along with the time t through differential calculation, comparing the limit indexes with the test system indexes, and if the limit indexes are not met, adjusting the test wind speed, and repeating the process until the lifting process of the test model 1 meets the test equipment indexes.
In addition, the actual test requires that the initial speed and the final speed of the heave/pitch coupling motion mechanism 2 are both 0, the limitation of the maximum stroke, the maximum acceleration and the like of the heave/pitch coupling motion mechanism 2 is required to be considered, and the influence of the ground effect on the area with the height larger than one time of the extension length of the aircraft is very small, so that the lifting process of the designed test model 1 is modified according to the limitation of the heave/pitch coupling motion mechanism 2 in the area with the height larger than 1 time of the extension length of the aircraft, and the acceleration and deceleration sections are added, so that the influence of the mechanism on the test is reduced as much as possible while the actual test requirement is met. The taking-off and landing process of the test model 1 designed in the test is shown in fig. 2, and the designed taking-off and landing process is different due to different real aircrafts, so that the taking-off and landing process is required to be designed according to specific parameters of the real aircrafts: first, the lift coefficient of the ground of a real airplane needs to be determined
And the parameters of the wing area S, the ground leaving speed V of the real airplane is calculated according to the formula (7) l0 ，
In (7)Wρ is the air density, which is the takeoff weight of the real aircraft.
As engineering estimation, the real aircraft is approximately considered to perform uniform acceleration linear motion in the whole running process, and then the ground running distance of the real aircraft is calculated according to formulas (8) - (9)
And time->
, in the formula />
The running friction coefficient of the real aircraft;
wherein g is the gravity acceleration,
is the average of the available thrust, +.>
。
When calculating the distance and time of the accelerating and ascending section of the real airplane, the speed V of the real airplane when ascending to the height of 15m is considered H =1.3
V l0 Finding the average speed of the aircraft during the whole take-off process +.>
The method comprises the following steps:
searching the maximum available thrust curve graph to obtain the average speed of the accelerating ascending section of the real airplane
Corresponding available thrust
Considering the aboveThe climbing angle gamma of the lifting section is not large, and the lifting force of a real airplane can be consideredLEqual toWThe corresponding lift coefficient is calculated as:
according to the lift coefficient C corresponding to the real aircraft L Value, find true aircraft resistance coefficient C from take-off pole graph D Calculating the value of the drag D and the average residual thrust (delta T) of the real aircraft av The method comprises the following steps:
obtaining the distance between the accelerating and ascending sections of the real airplane according to the steps (14) - (15)
And time->
，
After the parameters are obtained, the real aircraft attack angle and the horizontal speed are designed, the real aircraft attack angle only changes in the process of lifting the front wheels in the process of taking off, the horizontal speed is uniform acceleration movement in the processes of accelerating running and accelerating rising, and the real aircraft attack angle is increased from 0 DEG to the tail protection attack angle at a uniform speed
Duration of time period of (2)Is->
Angular velocity of it
The obtained horizontal speed of the real airplane comprises the following steps: horizontal direction speed of each time interval during acceleration running>
And horizontal direction speed of each time interval during acceleration of ascent +.>
, wherein ,/>
The design of the actual aircraft course is completed for the ith time interval in the whole take-off process of the actual aircraft.
Step two, a balance support rod is arranged on the heave/pitch coupling motion mechanism 2, a strain balance is arranged in the test model 1, one end of the balance support rod penetrates through a shell of the test model 1 to be connected with the strain balance, a measuring end of the strain balance is connected with the interior of the test model 1, a data line of the strain balance is connected with a wind tunnel acquisition system, a side-mounted floor 3 is arranged near the central position of a wind tunnel opening test section 4, and the motion center of the heave/pitch coupling motion mechanism 2 coincides with the reference center of the test model 1.
Step three, under the condition that the wind tunnel stops, the test model 1 is adjusted to reach the expected initial attack angle
Height from ground->
. Starting a heave/pitch coupling motion mechanism 2 to enable a test model 1 to perform forced motion according to a preset lifting process, acquiring each voltage signal of six-element load of the test model 1 in each process under a windless state by adopting a six-component strain balance, and acquiring the attack angle and the departure angle of the test model 1 by adopting an encoder and a height sensorA voltage signal of ground level.
And fourthly, starting a wind tunnel, starting a heave/pitch coupling motion mechanism 2 after the wind speed reaches a preset wind speed, enabling the test model 1 to perform forced motion according to preset lifting courses, acquiring each voltage signal of six-element load of the test model 1 in each course under the wind-up state by adopting a six-component strain balance, and acquiring voltage signals of the attack angle and the ground clearance of the test model 1 by adopting an encoder and a height sensor.
And fifthly, processing the acquired six-element load voltage signal data to acquire aerodynamic force and moment loads of the test model 1. Firstly, respectively carrying out filtering treatment and corresponding phase subtraction on balance original measured values acquired in windy and windless states, then carrying out balance formula iteration and dimensionless treatment to obtain six-element aerodynamic coefficients, and finally respectively converting voltage signals of an attack angle and a ground clearance of a test model acquired by an encoder and a height sensor into a pitching axis angle signal and a test model 1 height signal.
Example 2
The embodiment realizes the simulation of the taking-off and landing process of the airplane through forced movement, directly obtains the unsteady aerodynamic coefficient influenced by dynamic parameters such as the continuous change of the heave speed and the ground clearance in the taking-off and landing process of the test model 1, obtains the change process of the normal force coefficient and the pitching moment coefficient with time in the taking-off and landing process of the test model 1 shown in fig. 3-4, and provides basis for analyzing the influence of each dynamic parameter and the ground effect on the taking-off and landing of the airplane.
Claims (4)
1. A wind tunnel test method for measuring an unsteady aerodynamic coefficient in an aircraft take-off and landing process is characterized by comprising the following steps:
step one: the taking-off and landing processes of the real aircraft are divided into a plurality of micro-elements, the test model is guaranteed to be similar to the geometrical appearance of the real aircraft, and because the wind speed is fixed, the Stokes Ha Ershu in each micro-element time period are equal, namely the dimensionless time constants in each micro-element time period are equal, namely:
in the formula (1)
Is a dimensionless time constant, < >>
Time interval of minute for taking off and landing process of real airplane,/-for real airplane>
Is the real airplane flying speed, & lt + & gt>
Reference length for real aircraft, < >>
Time interval of taking off and landing process infinitesimal for test model,/-for test model>
For the test model speed, i.e. test wind speed,/->
For the reference length of the test model, the time interval for obtaining the landing process infinitesimal of the test model according to the above formula is as follows:
obtaining the time interval of the taking-off and landing process microelements of the test model through the method (2), further obtaining the motion time process of the test model, and obtaining the attack angle of each time interval of the test model in the wind tunnel through calculation
Angular velocity->
Angular acceleration->
Ground height +.>
The parameters of the model are shown as the formula (3) to the formula (6), so that an ideal lifting process of the test model is obtained;
wherein ,
for the angle of attack of a real aircraft per time interval, < >>
The ground clearance height of each time interval of a real airplane; because the test heave/pitch coupling motion mechanism needs to control the parameters of the ground clearance and the attack angle of the test model at each moment to enable the test model to move in the wind tunnel according to the preset process, the test model process needs to be dispersed into points with the time interval of 0.01s to obtain the ground clearance of the test model>
Angle of attack->
Obtaining limit indexes of the maximum pitch angle speed and the maximum heave speed in the process of simulating the take-off and landing process through differential calculation, comparing the limit indexes with the test system indexes, if the limit indexes are not met, adjusting the test wind speed, and repeating the process until the take-off and landing process of the test model meets the test equipment indexes;
step two, installing a balance support rod on the heave/pitch coupling motion mechanism, installing a strain balance in the test model, enabling one end of the balance support rod to penetrate through a test model shell and be connected with the strain balance, enabling a measurement end of the strain balance to be connected with an inner cavity of the test model, enabling a data line of the strain balance to be connected with a wind tunnel acquisition system, and installing a side-installed floor near the central position of a wind tunnel opening test section;
step three, under the condition that the wind tunnel stops, adjusting the test model to reach the expected initial attack angle
Height from ground->
Starting a heave/pitch coupling motion mechanism to enable the test model to perform forced motion according to a preset lifting process, acquiring each voltage signal of six-element load of the test model in each process under a windless state by adopting a six-component strain balance, and acquiring voltage signals of attack angle and ground clearance of the test model by adopting an encoder and a height sensor;
starting a wind tunnel, starting a heave/pitch coupling motion mechanism to enable the test model to perform forced motion according to a preset lifting process after the wind speed reaches a preset wind speed, acquiring each voltage signal of six-element load of the test model in each process under the wind-up state by adopting a six-component strain balance, and acquiring voltage signals of attack angle and ground clearance of the test model by adopting an encoder and a height sensor;
and fifthly, processing the acquired six-element load voltage signal data to acquire aerodynamic force and moment load of the test model, firstly, respectively carrying out filtering processing on the original measurement value of the balance acquired in windy and windless states and subtracting corresponding phases, then carrying out iteration of a balance formula and dimensionless processing to obtain six-element aerodynamic coefficients, and finally, respectively converting the voltage signals of the attack angle and the ground clearance of the test model acquired by the encoder and the height sensor into a pitching axis angle signal and a test model height signal.
2. The wind tunnel test method for measuring unsteady aerodynamic coefficient in taking off and landing process of aircraft according to claim 1, wherein in the first step, since actual aircraft is different, the designed take off and landing process is also different, and the take off and landing process is required to be designed according to specific parameters of the actual aircraft: first, the lift coefficient of the ground of a real airplane needs to be determined
And the parameters of the wing area S, the ground leaving speed V of the real airplane is calculated according to the formula (7) l0 ，
In (7)WThe takeoff weight of a real aircraft is represented by ρ, and the air density is represented by ρ;
as engineering estimation, the real aircraft is approximately considered to perform uniform acceleration linear motion in the whole running process, and then the ground running distance of the real aircraft is calculated according to formulas (8) - (9)
And time->
, in the formula />
The running friction coefficient of the real aircraft;
wherein g is the gravity acceleration,
is the average of the available thrust, +.>
；
When calculating the distance and time of the accelerating and ascending section of the real airplane, the speed V of the real airplane when ascending to the height of 15m is considered H =1.3
V l0 Finding the average speed of the aircraft during the whole take-off process +.>
The method comprises the following steps:
searching the maximum available thrust curve graph to obtain the average speed of the accelerating ascending section of the real airplane
Corresponding available thrust->
Considering that the climbing angle gamma of the ascending section is not large, the lifting force of a real airplane can be consideredLEqual toWThe corresponding lift coefficient is calculated as:
according to the lift coefficient C corresponding to the real aircraft L Value, find true aircraft resistance coefficient C from take-off pole graph D Calculating the value of the drag D and the average residual thrust (delta T) of the real aircraft av The method comprises the following steps:
obtaining the distance between the accelerating and ascending sections of the real airplane according to the steps (14) - (15)
And time->
，
After the parameters are obtained, the real aircraft attack angle and the horizontal speed are designed, the real aircraft attack angle only changes in the process of lifting the front wheels in the process of taking off, the horizontal speed is uniform acceleration movement in the processes of accelerating running and accelerating rising, and the real aircraft attack angle is increased from 0 DEG to the tail protection attack angle at a uniform speed
Is +.>
Its angular velocity +.>
The obtained horizontal speed of the real airplane comprises the following steps: horizontal direction speed of each time interval during acceleration running>
And horizontal direction speed of each time interval during acceleration of ascent +.>
, wherein ,/>
The design of the actual aircraft course is completed for the ith time interval in the whole take-off process of the actual aircraft.
3. A wind tunnel test method for measuring unsteady aerodynamic coefficients during take-off and landing of an aircraft according to claim 1 or 2, wherein the center of motion of the heave/pitch coupled motion mechanism coincides with the reference center of the test model.
4. The wind tunnel test method for measuring unsteady aerodynamic coefficient in the taking-off and landing process of an aircraft according to claim 3, wherein in the first step, the designed test model taking-off and landing process is modified in a region with the aircraft lift height being more than 1 time of the expansion length according to the limitation of the heave/pitch coupling motion mechanism, and acceleration and deceleration sections are added, so that the influence of the heave/pitch coupling motion mechanism on the test is reduced as much as possible while the actual test requirement is met.
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