Jeff Hiller
                                                                                                                                                    COMSOL Employee
                                                         
                            
                                                                                                                                                
                         
                                                
    
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                                                Posted:
                            
                                6 years ago                            
                            
                                29 ago 2019, 13:39 GMT-4                            
                        
                        Updated:
                            
                                6 years ago                            
                            
                                30 ago 2019, 08:46 GMT-4                            
                        
                        
                                                    Hello Hadi,
There are several ways the length of the channel could remain constant while you vary the angle of the bend: the bottom straight section could vary in length while the top straight section remains of constant length, or the top straight section could vary in length while the bottom straight section remains of constant length, or both straight sections could vary in length; so you have some decision to make there.  Also, I presume that it is the midline of the microchannel that you want to keep of a constant length, but perhaps it is one of its edges; this is not entirely clear to me from your post.
In any case, you can implement any of those constraints by using the fact that the length of an arc of circle is 
 , where 
 is the angle expressed in radians and 
 is the radius, and specifying the length of either or both of the straight sections accordingly in terms of
.
Although in this simple case things are pretty straightforward to implement already, I should mention that geometric constraints will be a lot easier to implement when we release version 5.5 of the Design Module in just a few weeks. Stay tuned!
Best regards,
Jeff
    -------------------
    Jeff Hiller                                                
 
                                                
                            Hello Hadi,
There are several ways the length of the channel could remain constant while you vary the angle of the bend: the bottom straight section could vary in length while the top straight section remains of constant length, or the top straight section could vary in length while the bottom straight section remains of constant length, or both straight sections could vary in length; so you have some decision to make there.  Also, I presume that it is the midline of the microchannel that you want to keep of a constant length, but perhaps it is one of its edges; this is not entirely clear to me from your post.
In any case, you can implement any of those constraints by using the fact that the length of an arc of circle is R \times \theta , where \theta is the angle expressed in radians and R is the radius, and specifying the length of either or both of the straight sections accordingly in terms of\theta.
Although in this simple case things are pretty straightforward to implement already, I should mention that geometric constraints will be a lot easier to implement when we release version 5.5 of the Design Module in just a few weeks. Stay tuned!
Best regards,
Jeff