Here is an example of what am looking to achieve:
Issue Type: Design Change- Automatically AssignAssignee: andrews.e
If someone creates the issue with the Issue type (Design Change) then it will automatically be assigned to - andrews.e
For Design Change issue type I have a separate workflow. So edited the workflow and added the Post Function - Update Issue Field. Please find the below snapshots.


I have added the post-functions and performed reindex. After that, I created the issue with my issue type (Design Change/Update) by default it's assigned to Project Lead.
Could you please suggest me on this....
Its bit urgent requirement -- Am using JIRA v 7.3.7