Generally Bansuri are tuned to kalyan scale, because in india it is played as top 3 holes closed as “Sa”
So if you assume it as “Sa” and Ratio 1:1
Then lower Ni will be 15:8 low than this “Sa”
Lower Dha will be lower 5:3
And lower Pa will be lower 3:2
And the tuning will be
3:2(1.5)/5:3(1.67)/15:8(1.88)/1:1(1)/9:8(1.13)/5:4(1.25)/45:32(1.41) (Pa-Dha-Ni-Sa-Re-Ga Tivra Ma)
Now if you play this bansuri with 3 holes closed as Sa than everything is OK.
But if you play this bansuri with all holes closed as Sa then the ratio changes (dividing all by 3:2,From Sa onwards divide by 3:2/2=3:4)
1:1(1)/10:9(1.11)/5:4(1.25)/4:3(1.33)/ 3:2(1.5)/5:3(1.67)/15:8(1.88)—(Sa-Re-Ga-Ma-Pa-Dha-Ni-Sa)
You see Re is Flat here if you play all holes closed as Sa
So to conclude tuning depends on how you play if you play 3 holes closed as Sa then tuning is shown above(first one), in short 3 holes closed then tuning kalyan and all holes closed Sa then tuning bilawal