How to model lobed mixer of jet exhaust in catia?

I want to create the model similar as shown in attached image. For that I have seen this tutorial https://grabcad.com/questions/how-to-create-a-turbofan-exhaust-mixer-in-catia-v5.
If you observe in tutorial model, the space between 2 lobes it gets reduced because the side walls are widening while joining the circle end. This reduces the space between 2 lobes. I dont want this to happen.
How to avoid this and make all lobed nozzles extend straightly towards the circle maintaining the same shape and without reducing the space between lobes.
I even tried giving the coupling points but i end up with flatness and sharp edges at circle end.
Please observe the space between 2 lobes. Can somebody give hints on this.
This model has to be created using blend or multisection using 2 curves only.
Thank you