How to know whether my PhD advisor knows the area of research? Ok here is the situation: My advisor gave me a paper about new model X. After reading and researching in X, I became very familiar with X and had many interesting ideas to extend its capabilities.  

One thing I noticed with my advisor is the lack of deep analysis over my ideas. By this, I mean a roadmap on how to get these ideas published, what are the things I need to polish/sharp/add to get it (most likely) accepted in top conference/journal. 

I handed him one draft of a paper, he didn't even doubt its findings; all his concern is to get it published somewhere in ranked C conferences; all he did was praising my writing (which is poor IMHO). What makes it even worse is the fact that I have seen some papers published in top conferences/journals with the same ideas I have (actually three ideas). 


  This makes me wonder: Does he really know X?


if yes, then why he did not provide constructive ways to sharp the ideas to get it published in a top conference? or maybe I am asking for something that he can't offer!
I suppose it is rather hard to give a satisfying answer to this question with the amount of information available. I mean, it's hard to estimate all the unknowns in this particular case. 


  if yes, then why he did not provide constructive ways to sharp the ideas to get it published in a top conference?


One could speculate in so many different ways; that he does not have the necessary grasp of the field to give meaningful critique is one speculation. Here's another plausible explanation; maybe he wants you to try flying on your own a bit, as a sink-or-swim approach. My supervisor did (and still does) this very often, I have almost too much freedom as to how I write, and what I write and to where I submit, then when the replies and reviews come in we sit down and improve on what I have done. Could be a similar approach

But to come back the question of how to know whether the supervisor is knowledgeable in a particular subject, here are some things that could be useful in the general case:


checking your supervisors publication record. Maybe the s/he has published articles on about this model before you even came to the group. Or maybe he was involved with an older but related model Y?
inquire you supervisor for his interest in the subject. If s/he gives you a paper about model X, all of a sudden then there is certainly a goal with that. To-the-point, effective communication might help you figure out his/her grasp of the field.


EDIT: In reply to the comment: 


  if I have too much freedom as to how I write, and what I write and to where I submit, then whats the point of supervision!


My supervisor often says that his job is to teach me how to do research, not provide me with knowledge or make sure I become successful/famous/rich... Your supervisor has ZERO responsibility in providing you the means to publish in top venues, IMHO. He merely has a responsibility to make sure you get the tools you need to be able to do the research you want to carry out, later on in life. 

As a side comment, I think your perspective to research might cause your frustration with your supervisor. Getting published in top venues is not a birth-right to all hard working grad students; and quite frankly, as a grad student where your articles get published have little to do with you or your work (at least in biomedical research).