Sure it is, but only a fraction stayed in the trenches, the rest was in the surrounding countryside. Murphy, using the better documented siege of Baghdad in 1638 thinks that adding gunners, diggers for the trenches and servants in general the numbers in the besieging force could reach 20.000.gagenater said:This is more than likely the case (an army of 50 - 60,000) However add in camp followers, civilian victualers, slaves and captives, animals and handlers, etc. and you can easily double this number. Any way you look at it even if 50 - 60,000 is the total number including all these other people it's still a heck of a big army for the era.
Now, however considering numbers we have two different problems, one is the military aspect, there we compare the size of the opposing armies (or armies in different periods, for instance) and here our first priority should be compare numbers of similar reliability. Unfortunately, given the peculiar structure of the Ottoman army, we have only paper strength figures of the Ottoman standing army in direct pay of the Sultan.
Now, considering the actual number of people involved in a force, including camp followers, is relevant for studying the development of supply systems. In that case we should detract from the 50.000-60.000 paper strength of the army a considerable number for deserters, sick, stragglers, detached garrisons, raiding parties, forage parties...In all I would be surprised if the Ottoman army (or their Christian opponents) could actually muster 30.000 men in the battlefield.