[badwolf]

I use an escape maneuver that works for me well.

Two ways you can be detected.
Pinging off your hull. Has a short range of detection. Avoid this by keeping range and exposing minimum hull. Bow or stern, not side on.

Sound detection. Has a decent range of detection. Keep at silent running 150 revs per minute when they are close.
Revs per minute is the true way to measure the maximum noise you make and so highest speed undetected. Different class subs travel different knots at 150 revs per minute. It's the revolutions the props go at that determines noise, not sub speed, knots.

Occasionally a destroyer will pass close overhead without dropping depth charges, as he's unaware you are there. Would be a bad mistake to go into flank speed, thinking he's on a run. So listen for charges hitting the water or the crew announce it or get to know how loud the ping is when he's directly above you.

So lets say, you are being attacked by 2 destroyers.
Both can't attack at the same time. One is closing in on you, while the other is a distance away circling for his turn.
You are on silent running, the destroyer passes above and drops it's charges. Instantly you go to flank speed. Up to you if you do a turn maneuver, but this will effect acceleration speed. I personally go into flank and dive if I can.
Keeping flank speed you follow the coarse the destroyer was on at attack, then note which way he turns. You turn the opposite way, 45 degrees approximately to get max speed/distance using his and your speed. Now, how long you keep flank speed is down to experience. But you drop into silent running when the second destroyers starts to close in. Usually straight after you have done your 45 degree course heading. I may be wrong, but I think the first destroyers props will keep you undetected when your very close behind.
The second destroyer should attack the place where you went into silent running, followed by the first again etc. Having not detected you for a while, the destroyers will break attack and go into search mode.
You must escape, fast as you can, before their search pattern picks you up again. This is most important when faced with multiple destroyers. Noise is harder to detect at longer ranges. So when the destroyers are a distance away, you can increase speed a bit above silent running, according to range. The amount of speed increase will come with experience.
If one comes close, drop into silent running and keep stern pointing towards the destroyer.
Happy hunting.