The military-industrial scientific research system of the academic master

"The Tu160 can indeed launch Kh15 supersonic anti-ship missiles at supersonic speeds, but the problem is not here..."

Faced with this problem, Jiang Jianjun scratched his head in distress:

“If a rotating launcher is installed, the thrown ammunition is actually located in a rather shallow position, and because the launcher structure occupies most of the space, the interior of the bomb bay is not a traditional rectangular or quasi-rectangular structure... These two The two factors work together, causing the static pressure flow situation to be relatively simple, and the weapon delivery process is similar to the conventional plug-in mode..."

"But after the rotating launcher is removed, the bomb bay of the Tu-160 will return to the traditional embedded rectangular structure... Our H-5 and H-6 that had bomb bays in the past were both subsonic aircraft, and they would only fly under the bomb The cabin is equipped with free-fall bombs, so it will not have any impact, but at supersonic speeds, the structure of the bomb cabin will affect the flow pressure distribution on the bottom surface, causing aerodynamic effects on the ammunition to be dropped. "

This section is relatively complicated.

"Will even heavy ammunition be affected?"

While they were talking, everyone had already left the tarmac and arrived at a factory not far away——

All along, Unit 41175 has been undergoing various tests and modifications here.

"As far as the flow field caused by a 300-ton aircraft is concerned, there will probably be no difference between 6-ton ammunition and 600-kilogram ammunition."

As Jiang Jianjun explained, he motioned to the two technicians who had just obtained the data to come forward.

The two men held several metal boxes of different colors, which actually corresponded to storage devices with different types of parameters.

Jiang Jianjun took out the orange one and connected it to a computer nearby.

Soon, a dense swarm of numbers appeared on the screen, which even made people feel dizzy at first glance.

But after a few clicks of the mouse, the abstract tabular data becomes intuitive and visual image content.

Only then did Jiang Jianjun continue to speak:

"The depth of the entire bomb bay in Figure 160 is nearly two meters, which is equivalent to an aspect ratio L/D of less than 6. The entire structure will become a deep cavity, thus forming a supersonic parallel bomb bay flow."

"In this case, the free flow is separated from the leading edge of the bomb cabin, and the shear layer separates the far-field free flow from the internal flow. The pressure distribution on the bottom of the bomb cabin is roughly uniform, only slightly higher at the trailing edge, and the target aircraft itself is relatively Safe, but the shear layer spanning the entire space structure will hit the rear wall of the bomb cabin, causing high-intensity aerodynamic noise, causing the bomb to vibrate during the throwing process..."

Qiao Chenqing is not an aerodynamics expert, but he can still understand the concise diagram.

Missiles generally adopt a thin-shell structure. Compared with iron bombs with rough skin and thick flesh, they cannot withstand too much torment. Excessive vibration is likely to cause damage to internal precision components.

Moreover, the verification bomb uses hydrogen-oxygen low-temperature propellant, so more care needs to be taken.

After thinking for a moment, he asked again:

"I have seen the rough parameters given by Academician Chang... The diameter of the verification bomb is slightly less than one meter. Can a partition be set up in the middle of the bomb cabin to only use the lower half of the space?"

“The chief’s idea is right, and this is the solution we are currently considering.”

Jiang Jianjun flattered the leader a little.

But his tone immediately changed:

"However... the closed bomb bay flow formed by the shallow cavity structure also has hidden dangers."

He said and brought up another diagram of the flow situation:

"In this case, the incoming flow separated from the front edge of the bomb bay but did not have enough energy to cross the bomb bay, causing the flow to hit the bottom of the bomb bay and separate again before reaching the rear wall of the bomb bay. The separated flow reattached to the bomb bay. The rear wall of the cabin forms a low-pressure area near the front wall and a high-pressure area near the rear wall.”

"One of these two obvious flow separation areas moves downstream of the forward wall, and the other moves upstream of the rear wall, thus generating a pair of opposite static pressure gradients, which reacts on the mount to produce a very large head-up moment. …”

"We have not yet verified the detailed aerodynamic shape of the missile, so it is difficult to assess the specific impact this torque will have. But even if we estimate it according to the best situation, it will significantly damage the ignition attitude of the missile, resulting in a large amount of fuel consumption after launch. Make adjustments that affect the range and ultimately the maximum speed achieved..."

Qiao Chenqing stared at the pictures on the computer screen for a long time before slowly exhaling:

"What's the worst case scenario?"

Jiang Jianjun wiped the sweat from his forehead:

"If the center of gravity of the loaded bomb is relatively far back and the flow intensity is relatively high, it may cause a complete loss of balance, or even cause the projectile that has left the bomb bay to be pushed back by the airflow again, and then hit the aircraft itself... …”

"..."

For a moment, everyone around them fell silent.

"I remember that the US military seemed to have a lot of aircraft. Was it lost for this reason?"

Seeing that the atmosphere was a little too heavy, Qiao Chenqing changed the topic slightly.

"That's right."

Jiang Jianjun replied:

“In some specific cases, even if the aircraft does not have a bomb bay in the physical sense, it will still form a closed flow similar to a shallow cavity structure under the wings or under the fuselage, causing the weapon to rise instead after being released, resulting in damage to the aircraft itself. ”

"However, the scale of the closed flow formed by the external mount is generally relatively small. As long as the ejection pylon is used to give the projectile an initial velocity and let it leave the dangerous position when released, the physically real bomb bay In particular, the downwash area formed by a large-sized bomb bay like the Figure 160 is very large, and it cannot be completely avoided by just relying on an ejection pylon..."

What Qiao Chenqing was thinking about at this time was actually another, longer-term issue.

"If this is the case, then the bomb bay of a tactical aircraft... is like that of the F22. Will it also face the same problem?"

After all, using the Tu-160 to throw air-launched cruise missiles is a one-time deal, and there is a high probability that it will not happen again.

But future fourth-generation fighter jets will need to be equipped in batches.

Jiang Jianjun nodded:

"So, on this topic, we are cooperating with several sister units such as the 601 Institute and the 611 Institute..."

Halfway through his words, he also saw Qiao Chenqing's face becoming increasingly livid.

So he quickly changed the topic:

"However, the size of the tactical aircraft is small after all, so the impact on the flow field after opening the bomb bay is relatively weak, not as serious as the situation we faced... In addition, the reason why we chose to use a shallow cavity bomb bay is because it has already We have some ideas to solve the problem, such as controlling the opening of the bomb bay door, and providing an initial negative angle of attack for the loaded bomb..."

"..."

Just when the atmosphere gradually reached a stalemate, a staff member hurriedly walked from outside the door, and then approached Jiang Jianjun and Qiao Chenqing:

"Chief, Mr. Jiang, we just received the documents from Academician Chang and the First Aerospace Academy."

Jiang Jianjun raised his eyes slightly:

"Are they the specific design parameters of the verification bomb?"

The staff member nodded, but did not leave.

Instead, he put a folder in his hand on the table:

"In addition...Mr. Chang also attached a letter, saying it was for the comrade responsible for the design of Haofa Group."

Jiang Jianjun was stunned after hearing this, and hesitantly opened the document in front of him.

Except for the header, there is only one sentence written on the entire A4 paper:

"The large-size bomb bay of the Tu-160 aircraft may cause flow field turbulence. For this problem, you can consider setting a spoiler on the leading edge of the bomb bay and setting a specific inclination angle on the trailing edge to alleviate this problem."