Question about power supplies

There are two formulas that my book gives to calculate maximum current and average current through a diode of a full wave rectifier. I was wondering what are those represented as on a diode's data sheet. the formulas are:

i dmax = IL(1 + 3.14×√Vp/2×Vr)

i av = IL(1 + 2×3.14 ×√Vp/2×Vr)

Vr is the ripple voltage peak to peak
IL is the load current
Vp is the peak output voltage of the supply

The values that i get when i calculate i av don't match anything that are provided on the diode's datasheets and i know that this diode can be used. i also see similar current values when i simulate rectifier circuit in p spice and look on current going through the diode. There is one big current surge, which is similar in value to the calculated value of i max, and smaller spikes that are similar in value to those of calculated i av.

Another question that i have is about voltage regulators

if you have a voltage regulator circuit and the load across it's output does not change, the voltage regulator circuit draws the same current, regardless of the input voltage put across it's input, right?

how can you simulate a load that draws the same current regardless of the voltage applied across it's input in p spice?
i use p spice student version

I am not getting your question. Can you upload the datasheet and the specification of diode alongwith the pages of your book, you are refering.
You can simulate the load in Schematic tools of ORCAD.

Forget the question about diodes for now... Consider a transformer, full wave rectifier, capacitor and lm317 connected to the capacitor. about the load ... i am glad that i can do it .... BUT HOW? for example you have LM317 (look for data sheets on the web) configured to provide regulated output of 4 V and your load is 10 ohms. You can say that the load is drawing .4 amps and the whole regulation circuit is drawing .4 amps + currents that run across the external resistors in the regulation circuit ( let's say that it is 7.5 V with ripple voltage of 1V peak to peak ). Now, the voltage delivered to the voltage regulation circuit is not a smooth DC voltage because it has some ripple voltage, but the current drawn by voltage regulation circuit is the same whether the input voltage is 8 v or 7v. ORCAD in Pspice student version has no element called lm 317 so i have to model it with something that exists... but what?.

thanx